Add name column to ci_runner_taggings table

What does this MR do and why?

This MR adds a name column to ci_runner_taggings table, so that we don't rely on the cell-local tags table. It also adds logic to populate and keep up to date the field, based on the value from tags.

Changelog: other

References

• Add `tag_name` column to `ci_runner_taggings` t... (#570215 - closed)
• Fix runner tags to work with Cells (#467664)

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