network: add VP message type for stateful vote compression

[cce]

Summary

This follows #6351 by integrating it with the WebsocketNetwork implementation, using a new VP message tag.

Test Plan

New tests added to exercise table size negotiation & success + failure scenarios. Stateful encoder/decoder errors should still keep connection alive, switching off compression immediately and letting votes continue to pass through. Ran swarm performance tests.

[codecov]

Codecov Report

❌ Patch coverage is 83.13253% with 42 lines in your changes missing coverage. Please review.
✅ Project coverage is 47.38%. Comparing base (495da8c) to head (6e1eeae).
⚠️ Report is 7 commits behind head on master.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
network/msgCompressor.go	72.15%	17 Missing and 5 partials ⚠️
config/localTemplate.go	0.00%	15 Missing ⚠️
network/wsPeer.go	94.44%	4 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6466      +/-   ##
==========================================
- Coverage   47.44%   47.38%   -0.07%     
==========================================
  Files         666      659       -7     
  Lines       88310    88415     +105     
==========================================
- Hits        41900    41896       -4     
- Misses      43649    43748      +99     
- Partials     2761     2771      +10     

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[algorandskiy]

Good docs update!