Don't use (or need) Content (again) in ViewEntityAction

The only thing is was used for at this point was to lookup
a label.

To make this most efficient, we can put the label into
parser output and get it via an OutputPage property.

Article::view takes care of everything else, in terms
of permission checking, resolving revisions for diffs, etc.

For page view:
* 5800 ms response time, 64630824 memory usage (with this patch)
* 6679 ms response time, 64812472 memory usage (on master)

On purging my large(ish) item, using xdebug, with this patch
it appears ~200ms slower (probably due to handling language fallback
there) and slight improvement to memory usage.

The improvement to page view response time is worth it.

Bug: T78265
Bug: T77134
Change-Id: I8d3f3ccdf82b9a6556df922b09f14370597280b8
Apply LanguageFallback (variants) for getLabel in lua

we had this before we changed to use the label lookup.

maybe we also want a method to request labels without
resolving fallback or something else? regardless of
whatever / however else we want, i think we should
keep getLabel behavior consistent with what it was before.

also add test case to check that language fallback is
applied for lua entity serialization for variant languages.

Change-Id: I07e698b9fec99c612f0d52fc337396360b765b66