The support for rest_total_hits_as_int has already been merged to 6x
in #35848 so this change adds this new option to master. The plan was
to add this new option as part of #35848 but we've decided to wait a few
days before merging this breaking change so this commit just handles
the new option as a noop exactly like 6x for now. This will allow
users to migrate to this parameter before #35848 is merged.
Relates #33028