TezosX/L2Node: add tezos bootstrap account to make config command

What

Add bootstrap account to make kernel config command, and test helpers.

Fix L2-632

Why

We want to start using tezos account with the tezos runtime.

How

We reuse the parameters set for make l2 kernel config and use the data model set for TezosX (see https://linear.app/tezos/document/rfc-tezos-x-experimental-support-for-tezos-implicit-accounts-3a01bccfa990).

The modification to the tests helpers make use of the tez_bootstrap_accounts parameters. It was previously only used for multichain sequencers that activate tezlink. This MR extend that parameters to single EVM chains, when the with_runtimes parameters contains the Tezos runtime. This should have no impact on Tezlink tests (that use the multichain setup and the make l2 kernel config command), and no impact on Etherlink tests (which set with_runtimes = []).

Note on factorization: we do basically no factoring of code. It can come later IMO, when we know what's needed.

Manually testing the MR

We added a test. It's a bit over the top and weird to do, as it's mostly testing test helpers, but there are encoding involved, which is tricky to debug, so... maybe it'll help ?

dune exec etherlink/tezt/tests/main.exe -- --file tezosx.ml bootstrap

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
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