Classes that model enums in dart:ui typically name fields modelling the
enum values as `_kFooIndex`. This associated value matches the enum
value from embedder.h.

In #32408 we add a test that
verifies that dart:ui classes model the same set of values in the native
implementation, the web_ui implementation, and the embedder API. Testing
this is much simpler if we use consistent naming for all enum values.

Issue: #32408

…2412)

* Fix special character input on a selection

* Add test for composing when selection is active

Co-authored-by: Renzo Olivares <[email protected]>

Removes the `Index` suffix from kMoveCursorForwardByWord and
kMoveCursorBackwardByWord values in the SemanticsAction enum. These were
erroneously copied as-is from the private class members in the dart:ui
implementation in lib/ui/semantics/semantics.dart where the class
members refer to the enum index here. This removes the trailing `Index`
for consistency with the other enum members here.

This is also useful in the context of automated testing for API
consistency between these enums, the ones in dart:ui (native and web
implementations) and the embedder API.

Issue: flutter/flutter#101217