Fix runner tags to work with Cells

This issue serves to track the progress of #467197 (closed) in the &11702 epic.

Plan

• Create ci_runners_taggings partitioned table (#467197 - closed)
• Save taggings data to ci_runner_taggings (#472974 - closed)
• Backfill the new runner taggings table (#504647 - closed)
• Handle the FKs from ci_runner_taggings to tags (see spec/lib/gitlab/database/no_cross_db_foreign_keys_spec.rb): #470872 (comment 2382060671)
  • Add `tag_name` column to `ci_runner_taggings` t... (#570215 - closed)
  • Prepare app to populate ci_runner_taggings.name field
  • Backfill `ci_runner_taggings.tag_name` column (#570217 - closed)
  • Make ci_runner_taggings.tag_name column non-nul... (#573111) Add NOT NULL constraint on ci_runner_taggings.tag_name (with NOT VALID) - %18.6
  • Add index on ci_runner_taggings.tag_name column (#573112) Add index on ci_runner_taggings.tag_name column - %18.6
  • Validate NOT NULL constraint on ci_runner_taggi... (#573115) Validate NOT NULL constraint on ci_runner_taggings.tag_name - %18.7
  • Remove join from TaggableQueries.arel_tag_names... (#573113) Remove join from TaggableQueries.arel_tag_names_array - %18.7