EVM/Node: limit how long a transaction can live in the pool

What

Next: !12749 (merged).

Part. of #7109 (closed): Bound the time a transaction can live in the pool, i.e. removing it passed a timeout.

Why

The purpose is to have a cleaning routine inside the transaction pool and avoid unwanted congestions inside it.

How

Put a limit on how long can a transaction live inside the transaction pool. The limit was set to 3600 seconds/an hour, feel free to suggest a better number in a comment below.

Manually testing the MR

dune exec etherlink/tezt/tests/main.exe -- --file evm_rollup.ml evm tx_pool timeout

It'd be cleaner to write this test with txpool_content RPC (one of the item from #7109 (closed)) implemented. It should probably be tweaked in a follow-up issue #7123 (closed).

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR