Use hook name for pre-commit stages

* Since 3.2.0 the tool expects the stage name to be the same as
  the hook name. Deprecation warning is now issued to encourage
  the migration.

Signed-off-by: Viet-Hoa Do <viet-hoa.do@arm.com>

Approved-by: Anton Bondarenko <anton.bondarenko@arm.com>
Approved-by: Jens Elofsson <jens.elofsson@arm.com>