Scope the TextInput spannable cache to the React instance (#58869)

[zeyap]

Summary:

On Fabric, ReactEditText caches its spannable in TextLayoutManager keyed by react tag, and the shadow node's state keeps that tag as cachedAttributedStringId to re-measure against. The cache was a single process-global map keyed only by tag. React tags restart for every new React instance, so after a reload the old and new instances can use the same tags in the same map: the new instance can read the old instance's spannable, and when an old ReactEditText is finalized it removes the new view's entry. The next cached measure then fails checkNotNull in getOrCreateSpannableForText with "Required value was null".

This change gives each React instance its own spannable cache:

• TextLayoutManager keeps one map per ReactApplicationContext. FabricUIManager creates it in its constructor and removes it in invalidate().
• FabricUIManager.measureText passes its own context, so a cached measure only looks in that instance's map.
• ReactEditText writes to and evicts from the map of the context it was created with (ThemedReactContext.reactApplicationContext). Create, destroy, read and write all resolve the key through one helper, so a view's ThemedReactContext and FabricUIManager's ReactApplicationContext always hit the same map. After teardown, an old view's set or evict does nothing because its map is gone.
• A layout that started before invalidate() can still reach measureText after the map is removed. In that case the cached measure returns a 0x0 measurement instead of throwing, because the cache-id MapBuffer carries only the id and there is nothing to rebuild from. The result belongs to an instance that is going away. The same applies when finalize() has already evicted the tag while a background commit still measures it: the measure returns 0x0 instead of failing checkNotNull.

This replaces the previous version of this diff, where finalize() only evicted the spannable the instance itself had cached. Per-tag eviction still happens in finalize(), but now only within the view's own instance, where tags are never reused. I did not move eviction to onDropViewInstance: a commit whose layout is still running on a background thread can measure a TextInput after the UI thread has already processed that view's delete, so evicting right away would make that case much more common.

Changelog:
[Android][Fixed] - Fix TextInput measurement crash ("Required value was null") after a React instance reload, by scoping the cached TextInput spannables to the React instance

Reviewed By: zeyap

Differential Revision: D122870300

[meta-codesync]

@zeyap has exported this pull request. If you are a Meta employee, you can view the originating Diff in D122870300.