Support unixfs 1.5 inline metadata

[iand]

This is a port of ipfs/go-unixfs#117

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[codecov]

Codecov Report

Merging #317 (4ab7b86) into main (8ec71db) will increase coverage by 0.06%.
The diff coverage is 72.48%.

@@            Coverage Diff             @@
##             main     #317      +/-   ##
==========================================
+ Coverage   48.26%   48.33%   +0.06%     
==========================================
  Files         279      279              
  Lines       33538    33672     +134     
==========================================
+ Hits        16187    16275      +88     
- Misses      15672    15708      +36     
- Partials     1679     1689      +10     

Impacted Files	Coverage Δ
ipld/unixfs/pb/unixfs.pb.go	51.23% <38.88%> (-5.24%)	⬇️
ipld/unixfs/importer/balanced/builder.go	59.45% <66.66%> (+0.99%)	⬆️
ipld/unixfs/importer/helpers/dagbuilder.go	73.71% <81.81%> (+13.13%)	⬆️
ipld/unixfs/unixfs.go	75.18% <85.48%> (+3.35%)	⬆️
ipld/unixfs/importer/trickle/trickledag.go	53.78% <100.00%> (+0.19%)	⬆️
ipld/unixfs/io/dagreader.go	80.43% <100.00%> (+0.58%)	⬆️

... and 8 files with indirect coverage changes

[iand]

Abandoned