In #28691, schedule plans will be deleted when a repo's actions unit is
disabled. But when the unit is enabled, the schedule plans won't be
created again.
This PR fixes the bug. The schedule plans will be created again when the
actions unit is re-enabled
Fix #28157
This PR fix the possible bugs about actions schedule.
## The Changes
- Move `UpdateRepositoryUnit` and `SetRepoDefaultBranch` from models to
service layer
- Remove schedules plan from database and cancel waiting & running
schedules tasks in this repository when actions unit has been disabled
or global disabled.
- Remove schedules plan from database and cancel waiting & running
schedules tasks in this repository when default branch changed.