Tezt/Cloud/DAL: map scatters reaming stake

This MR adds the support of a reworked map(x,y,z) that, instead of mapping the remaining baking keys on a single baker, it maps it in a round robin fashion on z bakers.

Manually testing the MR

A bit tricky to test locally and not sure it worth spending GCP credits on that. Not sure the testing is very useful.

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