SlotFills: Use state for registry initialization

[Mamaduka]

What?

PR updates SlotFill providers to initialize context values via useState lazily. The code used the same initialization method but changed during TS refactoring - 821f4d4.

Why?

• Fixes react-compiler/react-compiler error - Expected the first argument to be an inline function expression.
• This is a valid pattern for initializing values. See https://tkdodo.eu/blog/use-state-for-one-time-initializations and https://x.com/dan_abramov2/status/1792555601106551229.

Testing Instructions

CI checks should be green.

Testing Instructions for Keyboard

Same.

[ellatrix]

Why can't it be useMemo( () => createSlotRegistry(), [] )?

[ellatrix]

Hm, read those articles, that's interesting.

[github-actions]

The following accounts have interacted with this PR and/or linked issues. I will continue to update these lists as activity occurs. You can also manually ask me to refresh this list by adding the props-bot label.

If you're merging code through a pull request on GitHub, copy and paste the following into the bottom of the merge commit message.

Co-authored-by: Mamaduka <mamaduka@git.wordpress.org>
Co-authored-by: ellatrix <ellatrix@git.wordpress.org>

To understand the WordPress project's expectations around crediting contributors, please review the Contributor Attribution page in the Core Handbook.

[ellatrix]

There's probably quite a few places where we're misusing useMemo

[Mamaduka]

There's probably quite a few places where we're misusing useMemo.

Unfortunately, it can't be avoided in large projects.

I've seen some unnecessary memoizations in the code. Hopefully, we'll have to worry less about this when the project starts using the react-compiler.