Rename endorsement in lib_delegate

Context

This MR rename the occurrences of endors* in lib_delegate (not in the tests).

The commit lib_delegate: update encoding in baking_highwatermarks allows the baker to read two possible highwatermarks format and write the new term attestations instead of endorsement in the baker file.

The rest of this MR is mainly a sed to rename endors in attest.

Manually testing the MR

CI green

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)
• n/a Provide automatic testing (see the testing guide).
• n/a 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