fix(html): skip caching CSS of chunks in a cycle (fix #23628)

[hungateJoseph]

Description

fix #23628

With more than one HTML entry, a page could be built without some of its stylesheet links when the chunks it imports form a cycle, and which page lost which stylesheet depended on the order the entries were processed in.

getCssFilesForChunk stops at a chunk it is already visiting, which keeps the walk finite, but the list it then caches for the chunk that closed the cycle lacks the stylesheets of the chunk still being visited. That is fine for the entry being walked, since the visiting chunk adds its own stylesheets further up, but analyzedImportedCssFiles is shared by every HTML entry in generateBundle, so the next entry that reaches that chunk reuses the partial list.

This change only caches a chunk once every chunk it imports has a cached list of its own. Chunks that take part in a cycle are walked again for each entry instead of being cached; everything else is cached as before, so the ordering fix from #19143 and the cross-entry cases from #21298 / #22017 are unchanged.

I considered giving each HTML entry its own cache, which also fixes it, but that drops the cache for every chunk rather than only the ones in a cycle.

The new unit test builds index -> shared <-> feature and dashboard -> feature, and checks that dashboard still gets shared.css. It fails on main with ['feature.css', 'dashboard.css'] and passes with this change. I also ran the reproduction from the issue against this build: 10 of 10 builds link both stylesheets on both pages, where 8.3.1 lost one in most builds.

[sapphi-red]

Thanks!