improved shown keybindings in context menu

[jonah-iden]

What it does

This improves the visible keybindings in context menus by not showing keybindings that are inactive in the current context.

How to test

For example add a keybinding like this to some keybinding contribution

 {
        command: CommonCommands.UNDO.id,
        keybinding: 'z',
        when: 'notebookEditorFocused',
}

previously this was the always shown as Z in the context menu regardless of if a notebook editor was focused.

Now this should still normally be ctrl/cmd+z but when a notebook editor is focused it should show as Z

Follow-ups

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• As a reviewer, I agree to behave in accordance with the review guidelines

[msujew]

LGTM 👍