Fixes #6 Migrate RawKeyboardEvent and related implications according …

[aymswick]

…to Flutter recommendations described here: flutter/flutter#136419

I swapped out the Raw version for the recommended Hardware version, and updated onKey to onKeyEvent in our keyboard listeners' FocusNodes as instructed by the migration guide: https://docs.flutter.dev/release/breaking-changes/key-event-migration . I believe merging this PR will get everyone on Flutter 3.19 compiling again without breaking existing functionality, but welcome further examination and manual testing.

I believe this change has caused 3 tests to fail in the pluto_key_manager_event_test.dart file, and have included a comment there to reflect what I believe to be the cause and best course of action for now. I have tested the 3 failing test cases manually (irl with a bluetooth keyboard on macOS and Chrome) and everything behaves as expected. I will paste the comment here as well:

While key combos still work in the real world, these 3 tests are failing due to what I suspect is an incomplete deprecation/migration from focusNode onKey to onKeyEvent. Flutter 3.19 does not trigger our event for sendKeyUpEvent only, and I prefer not to switch these tests to sendKeyDownEvent as that may cause unexpected behavior such as pasting multiple times due to repeating key presses. It might also be fine.

Additionally, I have reached out on the relevant Flutter issue (first link in this comment) to provide more clarity on if this test is failing due to an incomplete Flutter migration.

[doonfrs]

Thank you @aymswick for your great effort I will merge it first to allow the build then I will check the failed tests.