fix: test and handle identity CIDs

[rvagg]

Also be more explicit with CAR storage options.

Depends on:

• fix: test and handle identity CIDs, expose more testutils ipld/go-trustless-utils#10
• testutil: relax DirEntry usage for non-dag-pb ipfs/go-unixfsnode#69
• fix: traverser should skip over identity CIDs ipfs/go-graphsync#438

The graphsync one being the most tricky to get over the line and released. If it ends up being too much hassle I'll comment out the test here so it passes and work on that separately.

[codecov-commenter]

Codecov Report

Merging #426 (1535a73) into main (1c31d7c) will decrease coverage by 0.34%.
The diff coverage is 45.61%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #426      +/-   ##
==========================================
- Coverage   76.42%   76.09%   -0.34%     
==========================================
  Files          85       84       -1     
  Lines        6287     6320      +33     
==========================================
+ Hits         4805     4809       +4     
- Misses       1237     1256      +19     
- Partials      245      255      +10     

Files Changed	Coverage Δ
cmd/lassie/fetch.go	30.97% <0.00%> (-0.87%)	⬇️
pkg/internal/testutil/gen.go	62.69% <ø> (-1.43%)	⬇️
pkg/storage/deferredstoragecar.go	59.32% <38.23%> (-12.45%)	⬇️
pkg/internal/itest/testpeer/peerhttpserver.go	67.88% <50.00%> (-1.06%)	⬇️
pkg/internal/itest/testpeer/generator.go	75.00% <100.00%> (ø)
pkg/storage/cachingtempstore.go	74.69% <100.00%> (+0.15%)	⬆️
pkg/storage/duplicateaddercar.go	92.50% <100.00%> (+0.39%)	⬆️

... and 5 files with indirect coverage changes