EVM/Eval: cleanup the main runner loop

Context

The main eval loop is inherited from Revm tests, which is a big function with 3 imbricated for loops. This MR makes it a bit more readable by decomposing it into sub functions.

This is a prerequisite for a follow-up MR that will implement the support for Multitests, as it will reshuffle a bit the loop.

Manually testing the MR

This is only a refactoring, so check the results from the testsuite before and after.

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