move ipld/unixfs from gogo protobuf

[gammazero]

Gogo protobuf is deprecated. Move ipld/unixfs away from it.

• Kubo PR with this change: boxo with non-gogo unixfs kubo#10706
  • Note: Confirmed kubo with the change generates same CIDs as kubo without.

[codecov]

Codecov Report

Attention: Patch coverage is 57.03704% with 58 lines in your changes missing coverage. Please review.

Project coverage is 60.56%. Comparing base (9e4f046) to head (97711dc).

Files with missing lines	Patch %	Lines
ipld/unixfs/pb/unixfs.pb.go	57.03%	56 Missing and 2 partials ⚠️

@@           Coverage Diff           @@
##             main     #840   +/-   ##
=======================================
  Coverage   60.55%   60.56%           
=======================================
  Files         244      244           
  Lines       31136    31177   +41     
=======================================
+ Hits        18855    18882   +27     
- Misses      10604    10618   +14     
  Partials     1677     1677           

Files with missing lines	Coverage Δ
ipld/unixfs/unixfs.go	79.93% <ø> (ø)
ipld/unixfs/pb/unixfs.pb.go	54.32% <57.03%> (+6.38%)	⬆️

... and 8 files with indirect coverage changes