Merge branch '365354-purge-legacy-bm-helpers-from-partition-helpers' into 'master'

Cleanup legacy background migration module usages from Partition helpers

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/116601



Merged-by: James Fargher <proglottis@gmail.com>
Approved-by: Mohamed Hamda <mhamda@gitlab.com>
Approved-by: Aakriti Gupta <agupta@gitlab.com>
Approved-by: Adam Hegyi <ahegyi@gitlab.com>
Approved-by: James Fargher <proglottis@gmail.com>
Reviewed-by: Mohamed Hamda <mhamda@gitlab.com>
Co-authored-by: Prabakaran Murugesan <pmurugesan@gitlab.com>