Add extra check for competing proof + sort by nonce on ring buffer

[sstanculeanu]

Reasoning behind the pull request

Proposed changes

Testing procedure

Pre-requisites

Based on the Contributing Guidelines the PR author and the reviewers must check the following requirements are met:

• was the PR targeted to the correct branch?
• if this is a larger feature that probably needs more than one PR, is there a feat branch created?
• if this is a feat branch merging, do all satellite projects have a proper tag inside go.mod?

[codecov]

Codecov Report

❌ Patch coverage is 25.00000% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 77.64%. Comparing base (0f0c82c) to head (a8fb98e).

Files with missing lines	Patch %	Lines
consensus/spos/bls/v2/subroundEndRound.go	0.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@                 Coverage Diff                 @@
##           feat/testnet-fixes    #7891   +/-   ##
===================================================
  Coverage               77.63%   77.64%           
===================================================
  Files                     885      885           
  Lines                  125570   125574    +4     
===================================================
+ Hits                    97490    97504   +14     
+ Misses                  21590    21580   -10     
  Partials                 6490     6490           

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