Components: Remove unnecessary act() from Button tests

[tyxla]

What?

This PR cleans up a few unnecessary act() calls and improves some of the Button tests.

Why?

When preparing our tests to work with React 18 we did a bunch of those act() calls. It's time to clean them up where possible.

How?

• We're using user.tab() instead of imperative element focus. Directly focusing an element is not something a user can do; they'd rather focus an element through clicking or tabbing. By using user.tab() we alter the tests to better resemble user behavior.
• We're removing await act( () => Promise.resolve() ); calls - they no longer seem to be necessary.

Testing Instructions

Verify tests still pass: npm run test:unit packages/components/src/button/test/index.tsx

Testing Instructions for Keyboard

None

Screenshots or screencast

None

[ciampo]

Code changes LGTM 🚀 Much cleaner than before!

CI will confirm if indeed the unit tests keep working as expected ⏳

[github-actions]

Flaky tests detected in 3ed0096.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/4074617664
📝 Reported issues:

• [Flaky Test] List #47632 in specs/editor/blocks/query.test.js
• [Flaky Test] should always expand single line selection #39787 in specs/editor/various/multi-block-selection.test.js