fix: add wsts::Point validation to vote-for-aggregate-key burn op

[hstove]

As noted in #4533, the vote-for-aggregate-key's check method doesn't validate the aggregate key used in the payload against wsts::Point, which can lead to issues if there are any discrepancies between Secp256k1PublicKey and Point. This PR adds validation against Point, along with the existing Secp256k1PublicKey check.

• Closes [BUG] VoteForAggregateKeyOp incorrectly validates aggregate public key #4533

[jcnelson]

Thanks @hstove for the quick turn-around on this!

[xoloki]

LGTM

[codecov]

Codecov Report

Attention: Patch coverage is 93.75000% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 82.91%. Comparing base (fec1cb5) to head (6b01281).
Report is 5 commits behind head on next.

Additional details and impacted files

@@            Coverage Diff             @@
##             next    #4536      +/-   ##
==========================================
- Coverage   83.16%   82.91%   -0.25%     
==========================================
  Files         453      453              
  Lines      327368   327398      +30     
  Branches      323      323              
==========================================
- Hits       272244   271457     -787     
- Misses      55116    55933     +817     
  Partials        8        8              

Files	Coverage Δ
...ainstate/burn/operations/vote_for_aggregate_key.rs	92.74% <93.75%> (+0.06%)	⬆️

... and 37 files with indirect coverage changes

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