Merge branch 'backfill-desired-sharding-key-small-table-incident_management_oncall_participants' into 'master' 

Add and backfill project_id for incident_management_oncall_participants

See merge request !184771



Merged-by: Omar Qunsul <oqunsul@gitlab.com>
Approved-by: Omar Qunsul <oqunsul@gitlab.com>
Co-authored-by: Shubham Kumar <shukumar@gitlab.com>