This commit introduces a C++/WinRT utility library and moves
ScopedResourceLoader into it. I decided to get uppity and introduce
something I like to call "checked resources." The idea is that every
resource reference from a library is knowable at compile time, and we
should be able to statically ensure that all resources exist.

PR Checklist

• Closes Produce a winrt-specific types library to hold some of our WinRT helpers without cluttering conhost #2146
• CLA
• Tests added/passed
• Requires documentation to be updated
• I've discussed this with core contributors already.

Details

This is a system that lets us immediately failfast (on launch) when a
library makes a static reference to a resource that doesn't exist at
runtime.

It exposes two new (preprocessor) APIs:

• RS_(wchar_t): loads a localizable string resource by name.
• USES_RESOURCE(wchar_t): marks a resource key as used, but is intended
  for loading images or passing static resource keys as parameters to
  functions that will look them up later.

Resource checking relies on diligent use of USES_RESOURCE() and RS_()
(which uses USES_RESOURCE), but can make sure we don't ship something
that'll blow up at runtime.

It works like this:

IN DEBUG MODE

• All resource names referenced through USES_RESOURCE() are emitted
  alongside their referencing filenames and line numbers into a static
  section of the binary.
  That section is named .util$res$m.

• We emit two sentinel values into two different sections, .util$res$a
  and .util$res$z.

• The linker sorts all sections alphabetically before crushing them
  together into the final binary.

• When we first construct a library's scoped resource loader, we
  iterate over every resource reference between $a and $z and check
  residency.

IN RELEASE MODE

• All checked resource code is compiled out.

Fixes #2146.

Macros are the only way to do something this cool, incidentally.

Validation Steps Performed

Made references to a bunch of bad resources, tried to break it a lot.

It looks like this when it fails:

App.cpp

36  static const std::array<std::wstring_view, 2> settingsLoadErrorsLabels {
37      USES_RESOURCE(L"NoProfilesText"),
38      USES_RESOURCE(L"AllProfilesHiddenText_HA_JUST_KIDDING")
39  };

WinRTUtils\LibraryResources.cpp(68)\TerminalApp.dll:
    FailFast(1) tid(1034) 8000FFFF Catastrophic failure
    Msg:[Resource AllProfilesHiddenText_HA_JUST_KIDDING not found in
      scope TerminalApp/Resources (App.cpp:38)] [EnsureAllResourcesArePresent]