Remove redundant locks from txpool

[cffls]

Description

Improve txpool performance by removing redundant locks.

Most changes were from #604, which added the locks for deeper level of control when debugging.

pprof before

runReorg used ~45% of CPU cycles.

pprof after

Usage of runReorg dropped to 12%.

Changes

• Bugfix (non-breaking change that solves an issue)
• Hotfix (change that solves an urgent issue, and requires immediate attention)
• New feature (non-breaking change that adds functionality)
• Breaking change (change that is not backwards-compatible and/or changes current functionality)
• Changes only for a subset of nodes

Nodes audience

In case this PR includes changes that must be applied only to a subset of nodes, please specify how you handled it (e.g. by adding a flag with a default value...)

Checklist

• I have added at least 2 reviewer or the whole pos-v1 team
• I have added sufficient documentation in code
• I will be resolving comments - if any - by pushing each fix in a separate commit and linking the commit hash in the comment reply
• Created a task in Jira and informed the team for implementation in Erigon client (if applicable)
• Includes RPC methods changes, and the Notion documentation has been updated

Cross repository changes

• This PR requires changes to heimdall
  • In case link the PR here:
• This PR requires changes to matic-cli
  • In case link the PR here:

Testing

• I have added unit tests
• I have added tests to CI
• I have tested this code manually on local environment
• I have tested this code manually on remote devnet using express-cli
• I have tested this code manually on mumbai/amoy
• I have created new e2e tests into express-cli

[marcello33]

Great!