fix: [#3126] Fix keyboard events in scene scope

[eonarheim]

===:clipboard: PR Checklist :clipboard:===

• [x] :pushpin: issue exists in github for these changes
• [x] :microscope: existing tests still pass
• [x] :see_no_evil: code conforms to the style guide
• [x] :triangular_ruler: new tests written and passing / old tests updated with new scenario(s)
• [x] :page_facing_up: changelog entry added (or not needed)

==================

Closes #3126

Fixes an issue where key events (and other event types) get stuck in the previous scene InputHost and cause issues when switching back. This state will never be useful and has lost relevancy after the scene has switched.

Changes:

• Adds a InputHost.clear() to clear previous scene event state
• Director clears the previous scene input host

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