Basic injector daemon binary

Context

This MR introduces a new binary which can run a standalone instance of the injector, independent of instantiations in rollup nodes. It aims to support manager operations, but for this MR only transactions are introduced (both transactions and contract calls). The design of this binary is outlined in #5589. The binary (marked experimental) is meant for stress-testing the injector on its own, particularly for reproducing issues with the injector, such as #5701 (closed).

Manually testing the MR

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