Composite: always await initial render setup in unit tests

[ciampo]

What?

Extracted from #65720

Always await for the initial render setup in Composite unit tests

Why?

Looking at the code, it looks like the correct thing to do is to await for that setup function to execute.

This change should improve test reliability (I think I've seen some flakiness around composite tests).

How?

By awaiting every call to the renderAndValidate utility in unit tests

Testing Instructions

Unit tests should continue passing (and if there was any flakiness, that should improve)

[github-actions]

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Co-authored-by: ciampo <[email protected]>
Co-authored-by: tyxla <[email protected]>

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[github-actions]

Flaky tests detected in 74ad0b4.
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/11142730036
📝 Reported issues:

• [Flaky Test] Navigates the items list via UP/DOWN arrow keys #64334 in /test/e2e/specs/site-editor/dataviews-list-layout-keyboard.spec.js

[tyxla]

Makes sense, let's do it 👍 🚀

Makes you wonder why we weren't awaiting in the first place 🤔