Rename endorsement in protocol storage

Context

This MR rename endors* occurrences from the context storage.

Manually testing the MR

For the Missed_endorsements table, we want to ensure that no entries exist when we switch protocols. At the end of each cycle, Delegate_missed_endorsements_storage.check_and_reset_delegate_participation is called on each delegate and remove their entry from the Missed_endorsements table.

On a last block of a cycle, check that for every delegate, their missed_slots and missed_levels are set to 0.

CI green for other checks.

Checklist

• n/a Document the interface of any function added or modified (see the coding guidelines)
• n/a 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