[web] Fix CapsLock keyevent

[ferhatb]

Description

The web engine, to prevent the crash and keep Tab key working no matter what the lock state is, sets metastate for locks during keydown until handling at framework level is clarified.

metaState as part of RawKeyEvent is currently not making a clear distinction between modifiers and lock states. For example the code requires that NumLock state be true when user presses NumLock key (it will crash otherwise). The lock state on the other hand, won't be set in a browser until keyup on some platforms (see https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/getModifierState).

Past issues,PRs related to this:
#45250
#46718
#14165

So if engine interprets metaState as persistent lock state such as NumLock, shortcuts break since the matcher will fail since there is no entry for NumLock+Tab or CapsLock+NumLock+Tab for example. Ideally? shortcuts should only consider lock states if it is explicitly provided to add specificity. The ambiguity of NumLock+key needs to be resolved to either mean Option1: a key is pressed when in NumLock state or Option2: key is pressed in combination with NumLock key at the same time. It should still allow a developer to distinguish between them by tracking keydown/keyup events.

Related Issues

flutter/flutter#66601

Tests

Added test case to e2etests/web/regular_integration_tests/test_driver/text_editing_integration.dart

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[nturgut]

Question: which framework integration test covers this case?

[ferhatb]

Question: which framework integration test covers this case?

Should be added to Tab e2e test after engine PR is in.

[nturgut]

As discussed earlier, the e2e test can also go in with this PR.

LGTM.

[ferhatb]

As discussed earlier, the e2e test can also go in with this PR.

LGTM.

Added test case to e2etests/web/regular_integration_tests/test_driver/text_editing_integration.dart

[nturgut]

Thanks for adding the integration test :)