feat: implement PublicDirectory conflict reconciliation

[matheus23]

This implements three functions:

• PublicDirectory::reconcile which takes two directories & reconciles all changes between them. Think of this as similar to get pull, but where conflicts in files are merged automatically via a simple tie-breaking mechanism on the file hash. The return value indicates whether and which files were affected by the automatic merge, if at all.
• PublicDirectory::merge, the underlying function for reconcile, but which doesn't take into account if one of the directories may have been "ahead" in history. Use only if you know what you're doing, otherwise opt for reconcile.
• PublicNode::causal_compare, the underlying function in reconcile that figures out whether one version of a node is "ahead" of another or behind, or if they're two conflicting versions and need to be merged.

[codecov]

Codecov Report

Attention: Patch coverage is 56.91057% with 53 lines in your changes are missing coverage. Please review.

Project coverage is 54.48%. Comparing base (7931ad6) to head (3ee27b4).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #426      +/-   ##
==========================================
+ Coverage   54.35%   54.48%   +0.12%     
==========================================
  Files          57       57              
  Lines        4003     4126     +123     
  Branches      980     1028      +48     
==========================================
+ Hits         2176     2248      +72     
- Misses       1191     1220      +29     
- Partials      636      658      +22     

Files	Coverage Δ
wnfs-hamt/src/diff.rs	19.46% <ø> (ø)
wnfs-hamt/src/node.rs	52.73% <ø> (ø)
wnfs-hamt/src/pointer.rs	20.45% <ø> (ø)
wnfs-nameaccumulator/src/name.rs	82.27% <ø> (ø)
wnfs-unixfs-file/src/balanced_tree.rs	80.48% <ø> (ø)
wnfs-unixfs-file/src/builder.rs	51.85% <ø> (ø)
wnfs-unixfs-file/src/protobufs.rs	0.00% <ø> (ø)
wnfs/src/private/file.rs	70.11% <ø> (ø)
wnfs-common/src/metadata.rs	29.50% <62.50%> (+4.97%)	⬆️
wnfs/src/public/node/node.rs	66.07% <81.57%> (+7.96%)	⬆️
... and 2 more

... and 1 file with indirect coverage changes