Draft: Set Migrations Job suffix to desired Chart version

Sets the Migrations Job suffix to the desired Chart version as specified in the spec, following the idea mentioned in gitlab-org/charts/gitlab#734 (comment 637939994).

This replaces the suffix consisting of the first 3 characters in the adapter hash. As surfaced in #962 (closed), this can be inconsistent, meaning that upgrading the GitLab (chart) version will generate a Migrations Job with the same name it used in the last version. This means Migrations are never run properly, and the upgrade gets stuck.

Using the desired Chart version in the suffix will better ensure uniqueness, and give a helpful human-readable indication of the version for which migrations were run.

Changelog: changed

Closes #962 (closed)