node-split poc: add proposal publish failed state

[kacpersaw]

Description

This PR adds support for new state PROPOSAL_PUBLISH_FAILED

Error handling improvements:

• identity/state.go: Added a new ProposalPublishFailed struct and its corresponding APIStateInfo method to handle proposal publish failures.
• miner/remote_proposals.go: Updated the identityStates interface to include a new Set method and used it to handle proposal publish failures in the build method. [1] [2]

[codecov]

Codecov Report

Attention: Patch coverage is 5.55556% with 17 lines in your changes missing coverage. Please review.

Project coverage is 77.2%. Comparing base (e6dea00) to head (49bbb0b).
Report is 3 commits behind head on node-split-poc.

Files with missing lines	Patch %	Lines
identity/state.go	0.0%	11 Missing ⚠️
miner/remote_proposals.go	14.2%	5 Missing and 1 partial ⚠️

Additional details and impacted files

@@               Coverage Diff                @@
##           node-split-poc   #6514     +/-   ##
================================================
- Coverage            77.2%   77.2%   -0.1%     
================================================
  Files                 342     342             
  Lines               45822   45839     +17     
================================================
+ Hits                35385   35391      +6     
- Misses               8324    8330      +6     
- Partials             2113    2118      +5     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.