…rent (e.g. Table) (flutter#185793)

## Issue

Fixes flutter#174133 (and the duplicate flutter#180337). Placing a widget that hosts
an `OverlayPortal` — most visibly `Slider`, but anything that calls
`OverlayPortalController.show()` before its `OverlayPortal` is mounted —
inside a `Table`/`TableRow` crashes during mount with:

```
'package:flutter/src/rendering/object.dart':
Failed assertion: line 2138 pos 12: 'child.owner == owner': is not true.

flutter#2  RenderObject.redepthChild
flutter#3  _RenderDeferredLayoutBox.redepthChildren           overlay.dart:2576
flutter#4  RenderObject.redepthChild
flutter#5  RenderObject.adoptChild
flutter#6  _RenderTheater._addDeferredChild                   overlay.dart:1312
flutter#7  _OverlayEntryLocation._addChild                    overlay.dart:2185
flutter#8  _OverlayPortalElement.insertRenderObjectChild      overlay.dart:2447
...
flutter#24 _TableElement.mount.<anonymous closure>...        table.dart:303
```

This is a regression introduced between Flutter 3.32 and 3.35.

## Root cause

`Table` defers calling `adoptChild` on its `RenderObject` children until
*every* row has been mounted (`_TableElement.insertRenderObjectChild` is
a no-op while `_doingMountOrUpdate`; the children are wired in later by
`_updateRenderObjectChildren`). Meanwhile `_OverlayPortalElement.mount`
runs `super.mount` (which "attaches" the layout surrogate to its parent
— but Table swallows it) and then immediately mounts the overlay child,
which causes the deferred-layout box to be adopted by the
`_RenderTheater`. The theater is attached, so the deferred box receives
an owner — *while the layout surrogate has none yet*.

When the theater calls `redepthChild(deferredBox)`, the deferred box's
`redepthChildren` unconditionally calls
`_layoutSurrogate.redepthChild(this)`, which trips the `child.owner ==
owner` assertion across that owner boundary.

## Fix

`_RenderDeferredLayoutBox.redepthChildren` now skips the cross-redepth
when the surrogate is not yet attached, mirroring the existing guard in
`_RenderLayoutSurrogateProxyBox.redepthChildren`:

```dart
if (_layoutSurrogate.attached) {
  _layoutSurrogate.redepthChild(this);
}
```

The depth invariant is restored when the surrogate is finally adopted by
its parent: `_RenderLayoutSurrogateProxyBox.redepthChildren` already
calls `redepthChild(_deferredLayoutChild)` once that child becomes
attached.

## Tests

Adds a regression test in `test/widgets/table_test.dart` placing an
`OverlayPortal` whose controller is `.show()`'d before mount (mirroring
`Slider`) inside a `TableRow`, asserting that no exception is thrown and
the overlay child is present.

Without this fix the new test reproduces the assertion. With this fix
`flutter test test/widgets/table_test.dart`,
`test/widgets/overlay_portal_test.dart`,
`test/widgets/overlay_test.dart`, `test/widgets/raw_tooltip_test.dart`,
`test/widgets/overlay_layout_builder_test.dart`, and
`test/material/slider_test.dart` all pass.

## Pre-launch Checklist

- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [x] I read and followed the [Flutter Style Guide].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I added new tests to check the change I am making.
- [x] All existing and new tests are passing.

[Contributor Guide]:
https://github.com/flutter/flutter/wiki/Tree-hygiene#overview
[Tree Hygiene]: https://github.com/flutter/flutter/wiki/Tree-hygiene
[Flutter Style Guide]:
https://github.com/flutter/flutter/wiki/Style-guide-for-Flutter-repo

---------

Co-authored-by: Victor Sanni <[email protected]>