Matches the structure used on Windows of assuming a directory format.

The following issues have been filed to track the handling of these enum values:

* Handle the UITouchTypeIndirectPointer enum value. https://github.com/flutter/flutter/issues/53696
* Handle the UITouchPhaseRegion enum values. https://github.com/flutter/flutter/issues/53695

No change in functionality. Only makes the iOS engine build on the latest
versions of Xcode and iOS SDK. The enum values cannot be used with the
API_AVAILABLE macro because the buildbots have not been updated yet.

Since the trace provider hasn't been created yet, it is not possible to
trace the creation of a trace provider using a TRACE_DURATION event (the
trace enabled and category check will always fail).  While this isn't
causing any urgent problems, remove it to set a good example for other
clients of tracing that might happen to reference this code.

This PR touches variable names, class names, and file names so it's significantly more risky than its predecessor https://github.com/flutter/engine/pull/17329

Due to file name changes, this PR is expected to change the license files.

We haven't rename `shell/gpu` to `shell/raster` yet. It should be optional but I think it's better to have `raster_surface_software.cc` than `gpu_surface_software.cc`.

Fix problem that using multi-engines, sometimes OpenGL would crash be cause of invalid EAGLContext (#17366)

1. Simple "GPU thread" to "raster thread" replacement.

2. Regex replace "GPU([\n\r\s]+//+ thread)" with "raster$1".

3. Regex replace "// gpu$" with "// raster".

4. Simple test change.

5. Run ci/format.sh

* Android change to match the google internal changes.

* Fix format.

* Revert format change, add super call.

* Remove comment for API version.

close() returns a nonzero in case of an error.  Old code had it log
only when *no* error happens on close, which is exactly the opposite
of what we want.

On Fuchsia, we can now get executable VMOs from trusted backing
filesystems.  This allows us to remove the use of replace_as_executable
in favor of opening files with `fdio_open_fd_at` with the
`OPEN_RIGHT_EXECUTABLE` flag and getting VMOs by calling
`fdio_get_vmo_exec`.

By moving the responsibility for executability into the filesystem, we
are able to remove `deprecated-ambient-replace-as-executable` from
component manifests for non-JIT runners (the JIT runners still call
replace_as_executable in Dart's allocator).  It wasn't abundantly clear
whether .cmx files for tests were used purely in AOT runtime
environments or also saw JIT usage, so I left those as-is.

For context: this is a second attempt at #16690, which was reverted
because it broke the Dart JIT runner.  The primary difference is that
this time around, we correctly handle absolute vs relative paths,
depending on whether library loading bottoms out in `fdio_open_fd` or
`fdio_open_fd_at`.  I've added additional assertions to help ensure any
new usages use the correct shape of path.

Testing: I verified locally that the flutter product runner works on
Astro, and also successfully ran the Dart JIT example test (which was
the thing blocking the google3 roll with the previous attempt at this
patchset).
Co-authored-by: NDrew Fisher <zarvox@google.com>

* [fuchsia] Add labels to Scenic nodes.

* [fuchsia] Skip creating Scenic nodes for identity Transforms.

* [fuchsia] Assign elevation to Scenic nodes based on paint order.

* [fuchsia] Create Scenic OpacityNodes at leaf nodes.

* [fuchsia] Composite PhysicalShapeLayers using Skia, except when they need to float above child views.

In that case, they will still need to be pulled
into separate Scenic nodes to be composited on top
of the child view[s].

* [fuchsia] Add tests for Fuchsia-specific layer behavior.

Inspect commands going to Scenic and make sure
they match what is expected.

Also, restructure code to need less member variables,
and other cleanups based on review feedback.

Removed a text input trait that causes VoiceOver to be incorrect when tapping a text input. (#17203)

This is a step toward aligning the API with macOS, and will make it easier to add the precompiled library later for release mode (since it can just be added to the project directory, without any code changes required for wrapper clients).

At the C API, uses a struct instead of individual arguments, mirroring a change that was already made on the Linux side to make the C API cleaner.

Functional changes in addition to the restructuring:

adds relative path support, as was recently added for GLFW
Uses wstring, rather than string, for paths; the conversion to UTF-8 is actually a potential problem on Windows, so pushing it into the embedding allows us the possibility of removing it later (if we can figure out a good solution at the embedder.h layer) without API breakage.
The old APIs used by the standard runner are left in place for now to avoid breaking the template on an engine roll. Once the framework template has been updated, the old API paths will be removed.

This reverts commit 2627634b.

Fixes a regression from #16944

Truncate error messages for the crash reporter to the maximum length permitted by the FIDL call (#17189)

Currently every Linux runner has this code to allow relative resource paths; this moves it into the framework so that any embedder can get this behavior without that code needing to be in the template.

Rolls buildroot to pick up std::filesystem support in our libc++

Fixes https://github.com/flutter/flutter/issues/52356

See https://github.com/flutter/flutter/issues/52372

This moves the Metal `GrContext` creation utilities from `GPUSurfaceMetal` into
a separate `IOSContext` object subclass. An analogue of this object was used in
the GL regime for the management of onscreen and offscreen contexts that were
not tied to the lifecycle of the `GPUSurface`. This pattern has now been
generalized for use with all backends that need a resource context
(`IOSContextGL` and `IOContextMetal`).

The platform views controller management in the `ExternalViewEmbedder` interface
implementation was repeated three times for [Metal][metal], [OpenGL](opengl) and
[Software](software) rendering. This repetition has been removed and a single
implementation present in the base `IOSSurface` and used on all platforms.
Addition of new client rendering APIs should not affect how the engine renders
into the platform view interleaving levels.

All rendering API selection logic has been moved into a single set of utilities
in `rendering_api_selection.h`. This enables the removal of a lot of code blocks
guarded by `FLUTTER_SHELL_ENABLE_METAL`. The remaining uses of this will be
removed when unified builds are enabled.

The Metal backend now also adds traces similar to the GL backend.

The `IOGLContext` has been renamed to `IOContextGL` to be more in line with the
convention used in this library.

Fixes https://github.com/flutter/flutter/issues/41827
Adds https://github.com/flutter/flutter/issues/52150

[metal]: https://github.com/flutter/engine/blob/1194ba2b218706a201c5d2c5325b55a5932546c5/shell/platform/darwin/ios/ios_surface_metal.mm#L55
[opengl]: https://github.com/flutter/engine/blob/1194ba2b218706a201c5d2c5325b55a5932546c5/shell/platform/darwin/ios/ios_surface_gl.mm#L95
[software]: https://github.com/flutter/engine/blob/1194ba2b218706a201c5d2c5325b55a5932546c5/shell/platform/darwin/ios/ios_surface_software.mm#L146

We no longer package AOT artifacts as discrete blobs. The portable ELF loader
from the testing library may be used instead.

Fixes https://github.com/flutter/flutter/issues/52263