Refactors CiUnlockArtifactsService from SQL to AR

What does this MR do?

This MR reconstructs the SQL query in execute to AR, and therefore the second point is not necessary:

1. Avoid manually constructing executed SQLs (can we use AR for that)
2. Call it on an appropiate model

Does this MR meet the acceptance criteria?

Conformity

• I have included changelog trailers, or none are needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.

#336894 (closed)