Fix remapped shortcuts not getting activated in succession

[arjunbalgovind]

Summary of the Pull Request

This PR fixes a scenario where a user could remap Alt+A->Ctrl+A, Alt+V->Ctrl+V and if you press Alt+A, release A and press V, Ctrl+V was not getting invoked. This was happening because when we fixed Alt+Tab style shortcuts in #3965, we changed the behavior such that we release the remapped modifier only after a key apart from the invoked shortcut's keys are pressed. When this would happen, we would reset the keyboard state to whichever keys should be physically pressed at that time, however we were sending all the keys including the latest pressed key (V in the example), with the KEYBOARDMANAGER_SHORTCUT_FLAG, because of which when the system received Alt+V it would not remap it to Ctrl+V. The fix involves removing the flag for that particular key event. We still keep the shortcut flag for all the key events before that so that we don't reinvoke the initial shortcut and cause an infinite recursion.
Comments have been updated to clarify the flag usage and two test cases have been added to capture the scenario.

PR Checklist

• Applies to Keyboard mapping cannot be activate continuously #4647
• CLA signed. If not, go over here and sign the CLA
• Tests added/passed

Validation Steps Performed

Added test cases and manually validated with the repro steps in the issue

[alekhyareddy28]

LGTM! Validated that it fires the new shortcut which has been remapped.

[arjunbalgovind]

@enricogior should I merge this normally? The first commit is the fix and the second commit is for test cases. I think the second commit depends on another PR in master so it would be better to only cherry-pick the first commit to stable.

[enricogior]

@arjunbalgovind
you can use "Rebase and merge", it will preserve the two commits.

[arjunbalgovind]

Merged. ac2a9de is the commit to be cherry-picked

[enricogior]

@arjunbalgovind
done.