fix(event): be robust against incomplete event implementations

[ph-fritsche]

What:

Assign the specific event properties and methods on the events instead of relying on the event constructors.

Why:

Some DOM implementations are incomplete. E.g. Jsdom lacks support for PointerEvent and it won't be implemented any time soon.
While initializing the events should be out of scope, events lacking the properties we correctly provide for init makes for a bad user experience and simply assigning the properties seems sufficient.

Closes #926

Return correct modifier state for Alt, Control, Meta and Shift per getModifierState.

How:

Replace the createEvent imported from @testing-library/dom with own implementation.

Checklist:

• Tests
• Ready to be merged

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Latest deployment of this branch, based on commit cb9e056:

Sandbox	Source
userEvent-dom	Configuration
userEvent-react	Configuration
heuristic-fermi-3hxbd6	Issue #926

[codecov]

Codecov Report

Merging #1009 (a46b4d7) into main (a46b4d7) will not change coverage.
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[github-actions]

🎉 This PR is included in version 14.4.0 🎉

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