Add support for parsing the dns_resolver feature bit

[TheBlueMatt]

This feature bit is used to indicate that a node will make DNS queries on behalf of onion message senders, returning DNSSEC TXT proofs for the requested names.

It is used to signal support for bLIP 32 resolution and can be used to find nodes from which we can try to resolve BIP 32 HRNs.

#3283 will want to use this, so after both PRs are merged we'll need one more commit to set the feature flag, but #3283 is already getting kinda big so keeping this separate.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 89.56%. Comparing base (d49a08a) to head (457b634). Report is 10 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3346      +/-   ##
==========================================
- Coverage   89.59%   89.56%   -0.03%     
==========================================
  Files         127      127              
  Lines      103438   103441       +3     
  Branches   103438   103441       +3     
==========================================
- Hits        92672    92651      -21     
- Misses       8049     8066      +17     
- Partials     2717     2724       +7     

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[dunxen]

Matches what's in bLIPs repo. LGTM