⛱ Optimize HTTP/2 & HPACK

[masaori335]

This is an umbrella issue for optimizing HPACK encoding & related changes.

I optimized HAPCK encoding, but changes are getting big. so I'll break down them small PRs and list up here.

This is performance improvement, so this doesn't block any release.

• Reduce malloc
  • Perf: Fix mis-usage of Arena in HPACK: Perf: Fix mis-usage of Arena in HPACK #6495
  • Introduce LocalBuffer: Introduce LocalBuffer #6528
  • Perf: Use LocalBuffer in HTTP/2: Perf: Use LocalBuffer in HTTP/2 #6536
  • Perf: Decode XPACK String Literal without Arena: -
• Optimize HPACK Table Lookup
  • Cleanups: Cleanup: Break down HpackIndexingTable::lookup() into static table lookup & dynamic table lookup #6509, Cleanup: Get rid of MIMEFieldWrapper from HPACK encoding #6520
  • Get rid of casecmp: Perf: Replace casecmp with memcmp in HPACK static table lookup #6521
  • Optimize Static Table Lookup: -
  • Optimize Dynamic Table Lookup: -
• Optimize HTTPHdr Conversion
  • Optimize HTTPHdr conversion of HTTP/2 to HTTP/1.1: Optimize HTTPHdr conversion of HTTP/2 to HTTP/1.1 #6545
  • Optimize HTTPHdr conversion of HTTP/1.1 to HTTP/2: Optimize HTTPHdr conversion of HTTP/1.1 to HTTP/2 #6635
• Misc
  • Get rid of snprintf() to get authority: -
  • Add HTTP/2 Pseudo Headers to Well-Know-Strings: -