[ColorPicker] Accessibility: Close only flyout with escape key

[jaimecbernardo]

Summary of the Pull Request

What is this about:
When the escape key is pressed in the Color Picker editor, only the adjust color flyout should be closed instead of the whole window.

What is include in the PR:
Some code blocking the global key event hook from processing the escape key if the flyout is open.
Also some code to end the current session before starting a new one if the user presses the shortcut again.

How does someone test / validate:
Press the escape key when the flyout is open.

Quality Checklist

• Linked issue: [Color Picker- Editor]: Whole Color Editor pop-up get closed when user press 'ESC' inside 'Adjust color pop-up'. #12097

[niels9001]

@jaimecbernardo FYI, I think you can reuse a lot of this PR's code to fix: #12093

Same issue, just for FancyZones

[jaimecbernardo]

@niels9001 ,
Thanks for the review and the heads up.
I think #12093 is a bit different. There's the issue of making tooltips dismissable through the use of the Escape key.

[mykhailopylyp]

LGTM. Created an issue to track repetitive press behavior. #12519