feat: make changes to BlockStore trait based on feedback

[appcypher]

This pull request addresses the following suggestions and feedback made at ipfs thing. Todo item 3 has been implemented in PR #257.

We want to limit wnfs dependency on libipld. Changing the codec type from IpldCodec to u64 lets us replace libipld with libipld_core in wnfs and wnfs-wasm crates. In a way this also removes the limitation of libipld::IpldCodec enum.

We think bytes::Bytes is a much more efficient way of getting bytes to and from a BlockStore (for BlockStores implementation that care about that sort of thing). Previously we used Cow<Vec<u8>> and we have considered Read/Write but bytes::Bytes is just more flexible. This change basically makes block storage and retrieval more efficient and flexible while maintaining no_std compatibility.

This PR implements the following features

• Replace IPLDCodec with u64.
• Remove wnfs dependency on libipld.
• Prefer bytes::Bytes to Vec<u8> in BlockStore interface.

Test plan (required)

• Testing

  scripts/rs-wnfs test

Closing issues

Fixes #251

[codecov]

Codecov Report

Merging #286 (fc2f35d) into main (3fb5392) will increase coverage by 0.06%.
The diff coverage is 14.58%.

@@            Coverage Diff             @@
##             main     #286      +/-   ##
==========================================
+ Coverage   60.41%   60.47%   +0.06%     
==========================================
  Files          40       40              
  Lines        2766     2763       -3     
  Branches      687      690       +3     
==========================================
  Hits         1671     1671              
+ Misses        625      622       -3     
  Partials      470      470              

Impacted Files	Coverage Δ
wnfs-common/src/utils.rs	75.86% <0.00%> (-5.62%)	⬇️
wnfs-hamt/src/diff.rs	57.01% <ø> (ø)
wnfs-hamt/src/hamt.rs	20.58% <ø> (ø)
wnfs-hamt/src/merge.rs	59.25% <ø> (ø)
wnfs-hamt/src/node.rs	55.03% <ø> (ø)
wnfs-hamt/src/pointer.rs	30.00% <ø> (ø)
wnfs/examples/private.rs	0.00% <0.00%> (ø)
wnfs/examples/privateref.rs	0.00% <0.00%> (ø)
wnfs/examples/public.rs	0.00% <0.00%> (ø)
wnfs/examples/tiered_blockstores.rs	0.00% <0.00%> (ø)
... and 16 more

[matheus23]

I'd say this should be a feat PR, since it changes the signature in one of our exposed traits.

[matheus23]

Nice. Love it.