The `DECSTBM` margins are meant to define the range of lines within which
certain vertical scrolling operations take place. However, we were applying
these margin restrictions in the `ScrollRegion` function, which is also used in
a number of places that shouldn't be affected by `DECSTBM`.

This includes the `ICH` and `DCH` escape sequences (which are only affected by
the horizontal margins, which we don't yet support), the
`ScrollConsoleScreenBuffer` API (which is public Console API, not meant to be
affected by the VT terminal emulation), and the `CSI 3 J` erase scrollback
extension (which isn't really scrolling as such, but uses the `ScrollRegion`
function to manipulate the scrollback buffer).

This commit moves the margin clipping out of the `ScrollRegion` function, so it
can be applied exclusively in the places that need it.

With the margin clipping removed from the `ScrollRegion` function, it now had
to be applied manually in the places it was actually required. This included:

* The `DoSrvPrivateReverseLineFeed` function (for the `RI` control): This was
* just a matter of updating the bottom of the scroll rect to the bottom margin
* (at least when the margins were actually set), since the top of the scroll
* rect would always be the top of the viewport.  The
* `DoSrvPrivateModifyLinesImpl` function (for the `IL` and `DL` commands):
* Again this was just a matter of updating the bottom of the scroll rect, since
* the cursor position would always determine the top of the scroll rect.  The
* `AdaptDispatch::_ScrollMovement` method (for the `SU` and `SD` commands):
* This required updating both the top and bottom coordinates of the scroll
* rect, and also a simpler destination Y coordinate (the way the `ScrollRegion`
* function worked before, the caller was expected to take the margins into
* account when determining the destination).

On the plus side, there was now no longer a need to override the margins when
calling `ScrollRegion` in the `AdjustCursorPosition` function. In the first
case, the margins had needed to be cleared (_stream.cpp 143-145), but that is
now the default behaviour. In the second case, there had been a more
complicated adjustment of the margins (_stream.cpp 196-209), but that code was
never actually used so could be removed completely (to get to that point either
_fScrollUp_ was true, so _scrollDownAtTop_ couldn't also be true, or
_fScrollDown_ was true, but in that case there is a check to make sure
_scrollDownAtTop_ is false).

While testing, I also noticed that one of the `ScrollRegion` calls in the
`AdjustCursorPosition` function was not setting the horizontal range correctly
- the scrolling should always affect the full buffer width rather than just the
  viewport width - so I've fixed that now as well.

## Validation Steps Performed

For commands like `RI`, `IL`, `DL`, etc. where we've changed the implementation
but not the behaviour, there were already unit tests that could confirm that
the new implementation was still producing the correct results.

Where there has been a change in behaviour - namely for the `ICH` and `DCH`
commands, and the `ScrollConsoleScreenBuffer` API - I've extended the existing
unit tests to check that they still function correctly even when the `DECSTBM`
margins are set (which would previously have caused them to fail).

I've also tested manually with the test cases in issues #2543 and #2659, and
confirmed that they now work as expected.

Closes #2543
Closes #2659

(cherry picked from commit 0c8a4df)

- Remember last-used string in the Find dialog in conhost (GH-2845)

  (cherry picked from commit bfb1484)

- Bugfix: TextBuffer Line Wrapping from VTRenderer (GH-2797)

  Change VT renderer to do erase line instead of a ton of erase chars

  (cherry picked from commit 8afc5b2)

- Add some retry support to Renderer::PaintFrame (GH-2830)

  If _PaintFrameForEngine returns E_PENDING, we'll give it another two
  tries to get itself straight. If it continues to fail, we'll take down
  the application.

  We observed that the DX renderer was failing to present the swap chain
  and failfast'ing when it did so; however, there are some errors from
  which DXGI guidance suggests we try to recover. We'll now return
  E_PENDING (and destroy our device resources) when we hit those errors.

  Fixes GH-2265.

  (cherry picked from commit 277acc3)

- Enable VT processing by default for ConPTY (GH-2824)

  This change enables VT processing by default for _all_ conpty clients. See
  GH-1965 for a discussion on why we believe this is a righteous change.

  Also mentioned in the issue was the idea of only checking the
  `VirtualTerminalLevel` reg key in the conpty startup. I don't think this would
  be a more difficult change, looks like all we'd need is a simple
  `reg.LoadGlobalsFromRegistry();` call instead of this change.

  **Validation Steps Performed**
  Manually launched a scratch app in both the terminal and the console. The
  console launch's output mode was 0x3, and the terminal's was 0x7. 0x4 is the `
  ENABLE_VIRTUAL_TERMINAL_PROCESSING` flag, which the client now had by default
  in the Terminal.

  Closes GH-1965

  (cherry picked from commit 1c412d4)

- Remove unwanted DECSTBM clipping (GH-2764)

  The `DECSTBM` margins are meant to define the range of lines within which
  certain vertical scrolling operations take place. However, we were applying
  these margin restrictions in the `ScrollRegion` function, which is also used in
  a number of places that shouldn't be affected by `DECSTBM`.

  This includes the `ICH` and `DCH` escape sequences (which are only affected by
  the horizontal margins, which we don't yet support), the
  `ScrollConsoleScreenBuffer` API (which is public Console API, not meant to be
  affected by the VT terminal emulation), and the `CSI 3 J` erase scrollback
  extension (which isn't really scrolling as such, but uses the `ScrollRegion`
  function to manipulate the scrollback buffer).

  This commit moves the margin clipping out of the `ScrollRegion` function, so it
  can be applied exclusively in the places that need it.

  While testing, I also noticed that one of the `ScrollRegion` calls in the
  `AdjustCursorPosition` function was not setting the horizontal range correctly
  - the scrolling should always affect the full buffer width rather than just the
    viewport width - so ...

Related work items: #23507749, #23563809, #23563819, #23563837, #23563841, #23563844

This PR removes the `GetConsoleCursorInfo` and `SetConsoleCursorInfo`
methods from the `ConGetSet` interface, and the `GetScrollingRegion`
method from the `SCREEN_INFORMATION` class. None of these methods are
used anymore.

PR #2764 removed the last usage of `GetScrollingRegion`. 

The `Get/SetConsoleCursorInfo` methods don't seem to have ever been used
in the time that the terminal code has been open source, so whatever
purpose they originally served must have been replaced a long time ago.

The `GetScrollingRegion` method was originally called from the
`ScrollRegion` function, but that usage was removed in PR #2764 when the
margin handling was moved to a higher level.

I've checked that the code still compiles.

Closes #9771