refactor: regtest controller cleanup

[fdefelici]

Description

This PR does some housekeeping around the bitcoin_regetest_controller module, removing some unused code (found while working on #6219):

• attempt args in BitcoinRegtestController::submit_operation(..) (and descendant method in tha call stacks)
• allow_rbf member in BitcoinRegtestController that is always initialized to true (simplify some internal branch logic)

NOTE: The PR is currenly built on top of #6219, which introduces some testing facilities. It will be rebased once that PR is merged.

Applicable issues

• fixes Refactor: Clean Up BitcoinRegtestController #6253

Additional info (benefits, drawbacks, caveats)

Checklist

• Test coverage for new or modified code paths
• Changelog is updated
• Required documentation changes (e.g., docs/rpc/openapi.yaml and rpc-endpoints.md for v2 endpoints, event-dispatcher.md for new events)
• New clarity functions have corresponding PR in clarity-benchmarking repo
• New integration test(s) added to bitcoin-tests.yml

[Jiloc]

LGTM! Just a comment about the modularization of the tests. I like it and I believe we can keep it. But the extra indentetion made the diff difficult to review :( ! If we are going to refactor other tests into their own modules in the future, I'd suggest to split the indentation change to its own commit. It will be easier to review the single commits intead of the final diff!

[codecov]

Codecov Report

Attention: Patch coverage is 28.70370% with 385 lines in your changes missing coverage. Please review.

Project coverage is 70.60%. Comparing base (381ee9b) to head (c1b02c2).

Files with missing lines	Patch %	Lines
...-node/src/burnchains/bitcoin_regtest_controller.rs	28.43%	380 Missing ⚠️
stacks-node/src/tests/epoch_205.rs	0.00%	2 Missing ⚠️
stacks-node/src/nakamoto_node/relayer.rs	0.00%	1 Missing ⚠️
stacks-node/src/tests/epoch_21.rs	0.00%	1 Missing ⚠️
stacks-node/src/tests/signer/v0.rs	0.00%	1 Missing ⚠️

❌ Your project check has failed because the head coverage (70.60%) is below the target coverage (80.00%). You can increase the head coverage or adjust the target coverage.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #6243      +/-   ##
===========================================
- Coverage    71.20%   70.60%   -0.60%     
===========================================
  Files          546      546              
  Lines       347235   347511     +276     
  Branches       323      323              
===========================================
- Hits        247236   245358    -1878     
- Misses       99991   102145    +2154     
  Partials         8        8              

Files with missing lines	Coverage Δ
stacks-node/src/burnchains/mocknet_controller.rs	68.98% <ø> (-0.15%)	⬇️
stacks-node/src/burnchains/mod.rs	62.50% <ø> (ø)
stacks-node/src/neon_node.rs	60.48% <100.00%> (-17.10%)	⬇️
stacks-node/src/node.rs	86.68% <100.00%> (ø)
stacks-node/src/tests/nakamoto_integrations.rs	10.11% <ø> (-56.19%)	⬇️
stacks-node/src/tests/neon_integrations.rs	3.14% <ø> (-54.32%)	⬇️
stacks-node/src/nakamoto_node/relayer.rs	55.84% <0.00%> (-22.43%)	⬇️
stacks-node/src/tests/epoch_21.rs	0.00% <0.00%> (ø)
stacks-node/src/tests/signer/v0.rs	0.00% <0.00%> (-33.07%)	⬇️
stacks-node/src/tests/epoch_205.rs	0.00% <0.00%> (ø)
... and 1 more

... and 372 files with indirect coverage changes

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