What

This MR does two things:

create a module Setup that contains all the generic function to setup the environment for Sequencer test (not evm_rollup.ml yet).
mode the only DAL test into a new file, and reuse this Setup

Why

evm_sequencer.ml is already big enough, let's start on a clean state.

Run the CI

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