feat(ipns): helper ValidateWithPeerID and UnmarshalIpnsEntry

[hacdias]

After my overly excited merge and revert of #292, I looked at the code and saw we were already duplicating existing code. E.g. the key extraction logic already existed and was being duplicated. This PR adds two helper functions ValidateWithPeerID and UnmarshalIpnsEntry. They already use existing functionality. I also added tests.

I did not include IpnsInspectEntry for the reasons here: #292 (comment) - it doesn't make sense for us to be adding it here since it is tightly related to the type we use in ipfs name inspect. We only created it in first place to simplify the type used by the RPC client in Kubo.

I also enabled a test that has been disabled for 5 years in 0320605. It seems to pass now, and reading the commit description, I don't think it is a problem due to the way Peer IDs are encoded nowadays.

Tested in Kubo here: ipfs/kubo#9867

[codecov]

Codecov Report

Merging #294 (f9b6003) into main (dc731ca) will decrease coverage by 0.02%.
The diff coverage is 21.42%.

❗ Current head f9b6003 differs from pull request most recent head 50d2bc2. Consider uploading reports for the commit 50d2bc2 to get more accurate results

@@            Coverage Diff             @@
##             main     #294      +/-   ##
==========================================
- Coverage   48.02%   48.00%   -0.02%     
==========================================
  Files         279      279              
  Lines       33439    33451      +12     
==========================================
  Hits        16059    16059              
- Misses      15694    15703       +9     
- Partials     1686     1689       +3     

Impacted Files	Coverage Δ
gateway/handler_ipns_record.go	0.00% <0.00%> (ø)
ipns/ipns.go	55.83% <23.07%> (-1.58%)	⬇️

... and 8 files with indirect coverage changes

[Jorropo]

LGTM once thoses minors things are fixed.