Adaptive inflation activation test with costaking

Context

This MR is a first step toward solving #5874 (closed). It extends !9068 (merged), on which it is stacked, by testing that costaking is allowed when adaptive inflation is expected to be active. !9240 (merged) is based on this MR, it extends this test by checking the effect of costaking on the total_frozen_stake.

Manually testing the MR

dune exec src/proto_alpha/lib_protocol/test/integration/main.exe -- --file test_adaptive_inflation_launch.ml

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