Ref T2450. This reorganizes code to improve performance.

Mostly, there are a lot of things which are unique per commit (author name, links, short name, etc), but we were rendering them for every line.

This often meant we'd render the same author's name thousands of times. This is slower than rendering it only once.

In 99% of interfaces this doesn't matter, but blame is weird and it's significant on big files.

Locally, __phutil_library_map__.php now has costs of roughly:

• 550ms for main content (from 650ms before the patch).
• 1,500ms for blame content (frrom 1,800ms before the patch).

So this isn't huge, is a decent ~20%-ish performance gain for shuffling some stuff around.