* Add CPU-only rendering mode for CanvasKit as a fallback

This implements the design in flutter.dev/go/handling-synchronous-keyboard-events for Android.

I started with Android, but this will be used for all platforms as we add them.

The related framework PR is: flutter/flutter#59358 (which has already landed)

iOS now matches Android behavior in that empty selections put the cursor at the start of the field.

* remove obsolete check

* FML_DCHECK flutter_view_ in methods that actually use it

Before this change, when we encounter an unhandles exception,
we see:

```
[00050.147083][37665][67367][klog] ERROR: [ERROR:flutter/shell/common/shell.cc(209)] Dart Error: Unhandled exception:
[00050.147087][37665][67367][klog] INFO: UnimplementedError
```

This doesn't help identify the root cause. Adding stack trace will help
the cause.

* Move CkCanvas to new JS-interop
* Make SkiaObject compatible with JS-interop; text bindings
* fix drawVertices

* Makes IOS dispatchs showOnCcreen action for header semantics nodes

* update

* format