[Merged by Bors] - double-merge malfeasance proof

[poszu]

Motivation

Closes #6341

Description

A malfeasance proof for when more than 1 merged ATX is published in a single epoch by a single equivocation set. Covers only the simple case when no checkpoint is involved. Support for checkpoint will come in following PRs

Test Plan

Added tests, skipped the test for when the first merged ATX is checkpointed - this should be IMO a syntactically invalid ATX.

TODO

• Explain motivation or link existing issue(s)
• Test changes and document test plan
• Update documentation as needed
• Update changelog as needed

[codecov]

Codecov Report

Attention: Patch coverage is 75.67568% with 27 lines in your changes missing coverage. Please review.

Project coverage is 79.8%. Comparing base (516fc47) to head (1871311).
Report is 1 commits behind head on develop.

Files with missing lines	Patch %	Lines
activation/wire/malfeasance_double_merge.go	77.1%	14 Missing and 7 partials ⚠️
activation/handler_v2.go	57.1%	4 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #6339     +/-   ##
=========================================
- Coverage     79.8%   79.8%   -0.1%     
=========================================
  Files          343     344      +1     
  Lines        44505   44613    +108     
=========================================
+ Hits         35548   35632     +84     
- Misses        6952    6972     +20     
- Partials      2005    2009      +4     

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[fasmat]

bors merge

[spacemesh-bors]

Pull request successfully merged into develop.

Build succeeded:

• ci-status
• systest-status