feat(txpool): StatsWithMinBaseFee

[jonastheis]

1. Purpose or design rationale of this PR

When the base fee changes, transactions which are now below the base fee, stay in the txpool as pending. However, since we use the amount of pending tx in the GPO to determine the current congestion level of the network, this wouldn't yield any meaningful information anymore.

This PR, therefore, introduces a function StatsWithMinBaseFee to the txpool so that the GPO can query the pending transactions that are meaningful right now.

2. PR title

Your PR title must follow conventional commits (as we are doing squash merge for each PR), so it must start with one of the following types:

• build: Changes that affect the build system or external dependencies (example scopes: yarn, eslint, typescript)
• ci: Changes to our CI configuration files and scripts (example scopes: vercel, github, cypress)
• docs: Documentation-only changes
• feat: A new feature
• fix: A bug fix
• perf: A code change that improves performance
• refactor: A code change that doesn't fix a bug, or add a feature, or improves performance
• style: Changes that do not affect the meaning of the code (white-space, formatting, missing semi-colons, etc)
• test: Adding missing tests or correcting existing tests

3. Deployment tag versioning

Has the version in params/version.go been updated?

• This PR doesn't involve a new deployment, git tag, docker image tag, and it doesn't affect traces
• Yes

4. Breaking change label

Does this PR have the breaking-change label?

• This PR is not a breaking change
• Yes