Feature/use effect cleanup delegate

[Freymaurer]

Update React.useEffect, React.useEffectOnce, React.useLayoutEffect and React.useLayoutEffectOnce to ensure proper cleanup function handling in case of empty body.

Closes #714

[Copilot]

Pull request overview

Fixes issue #714 where React.useEffect/useEffectOnce/useLayoutEffect/useLayoutEffectOnce, when given a body that only returns a cleanup function, was compiled by Fable so that the cleanup ran immediately during setup instead of being returned. The fix routes the unit -> (unit -> unit) overloads through a new System.Func<unit, (unit -> unit)> overload (and emit-based JS) so Fable cannot inline-invoke the returned cleanup.

Changes:

• Add Func<unit, (unit -> unit)> based overloads of useEffect/useEffectOnce/useLayoutEffect/useLayoutEffectOnce and delegate the unit -> (unit -> unit) overloads to them.
• Add tests (OnlyCleanup components) verifying that a body returning only a cleanup runs the cleanup on unmount; restructure existing tests into nested Components.UseEffect / UseEffectOnce / UseLayoutEffect / UseLayoutEffectOnce modules and split describe blocks per hook.
• Bump CHANGELOG to 3.3.3 and modify the playground demo.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
src/Feliz/React/React.fs	Adds Func-based overloads with explicit emitJsExpr; mass reformatting.
src/Feliz/CHANGELOG.md	Adds 3.3.3 release note for #714.
tests/Feliz/ReactBindings/UseEffect.test.fs	Refactors components into nested modules; adds OnlyCleanup regression tests.
tests/Feliz/ReactBindings/UseLayoutEffect.test.fs	Same restructuring + OnlyCleanup regression tests for layout effect variants.
playground/src/Components.fs	Replaces the lazy/Suspense demo with a small #714 reproduction; comments out LazyCounter.

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