WP Package: Replace keyCode with key in key event handling in the wp folder

[R1shabh-Gupta]

Trac ticket: https://core.trac.wordpress.org/ticket/63759

This PR replaces the deprecated keyCode property with key in key event handlers within the wp folder.

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Note

I'm not sure whether the virtual keyboard keys need to be replaced (check dfw.js). I haven't made any changes to them yet. Please let me know if this also needs to be updated.

[github-actions]

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