Mousemove fires outside canvas

[Riley-Howley]

Description

Fixes Issue: #12373
This PR addresses adding a bounds check on the ScreenSpaceEventHandler handleMouseMove this issue was only reproducible in Firefox. Checking to make sure the client is inside the bounds of the canvas solves this issue

When integration Cesium in existing application, if menus are overlayed on the canvas then in firefox the event is triggered even though its not in the canvas

Issue number and link

#12373

Testing plan

Using the given example in the Issue, after my change I tested in Firefox, and Chrome. Note: I did this on a Mac.

Automated tests were updated to have a valid boundingClientRect so that it passes the new check. Also added a new test to ensure the event is not fired when in the bounds of the canvas

Author checklist

• I have submitted a Contributor License Agreement
• I have added my name to CONTRIBUTORS.md
• I have updated CHANGES.md with a short summary of my change
• I have added or updated unit tests to ensure consistent code coverage
• I have updated the inline documentation, and included code examples where relevant
• I have performed a self-review of my code

[github-actions]

Thank you for the pull request, @Riley-Howley!

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