Use oghttp2 HTTP/2 codec

[alyssawilk]

Parallel to #21245
Switching to oghttp2 allows

• turning up UHV (Enable UHV only for Balsa and oghttp2 codecs #27377) so significantly more standards compliant and consistent header sanitization
• significantly better security pipeline for data plane (future-proofs against several zero days)

Theoretically no significant behavioral or performance differences (or we should turn them off =P)

[alyssawilk]

cc @birenroy we have any internal docs for the last two points we can link here?

[milton0825]

@alyssawilk what is the timeline for deprecating nghttp2?

[alyssawilk]

Probably about a year (longer than the normal reloadable flag deprecation process, but it's also a larger change) but we can theoretically add an option to compile it out sooner if it's problematic.

[alyssawilk]

Worth mentioning and unfortunately I forgot to link, #31086 switched the default to oghttp2 last quarter!

[milton0825]

We ran into issues with oghttp2 and I have created: #31710