Optimize Compose HTML EAP SSR rendering

[Clemens Koprolin (clemenskoprolin)]

This PR reduces rendering overhead in Compose HTML EAP string, streaming and hydrated-document rendering.

Performance changes include:

• Tag metadata: reuse builders and their precomputed tag flags.
• Attribute names: cache validated names in bounded renderer storage.
• Composition locals: cache static rendering locals and avoid a temporary provider map.
• CSS serialization: write declarations directly and convert common values to strings once.
• Raw-text content: emit validated content directly without rebuilding it.
• JVM text escaping: use native string searches and bulk copying for longer text.
• Start-tag results: reuse an immutable result for ordinary tags, keeping allocation predictable.
• Snapshots: render in the caller's snapshot instead of creating and disposing one per render.

Rendering now uses the caller’s current snapshot. State changes from content and synchronous effects remain there. Callers requiring consistent reads and isolated writes should enter a mutable snapshot.

In our benchmarks, this reduced the first render 13.3%, subsequent renders by 27.7% and reduced the allocated heap by 19.6%.

Involves CMP-10836

Testing

Run from the html directory:

./gradlew -Pcompose.html.eap.enabled=true \
  :html-core-eap:jvmTest \
  :html-core-eap:jsBrowserTest \
  :html-core-eap:wasmJsBrowserTest \
  :html-svg-eap:jvmTest \
  :html-svg-eap:jsBrowserTest \
  :html-svg-eap:wasmJsBrowserTest

Release Notes

N/A

[Oleksandr Karpovich (eymar)]

This change compromises readability for better performance.
Also, I see there is a cache - HtmlAttributeNameCache.

Is not the HtmlAttributeNameCache the more important change performance-wise?
Will it matter if we keep this function more readable but less optimized?

[Clemens Koprolin (clemenskoprolin)]

Good point, I'll benchmark that specific optimization.

[Clemens Koprolin (clemenskoprolin)]

You’re right: the cache is the more important optimization here, I'll restore it to be more readable.

[Oleksandr Karpovich (eymar)]

here too, should this be skipped when validate is false?

Also, below: requireHtmlParserStableTableElement ?