Version Control for Snippets: Development of the Migration Plan (MVP)

What does this MR do?

This MR creates the background migration that will create and populate snippet repositories based on the value of the file_name and content columns. TL;DR this code does not run the migration, it just introduces it.

The main problem with this migration is that the git actions introduce a time overhead in each iteration.

Basically, what we do is, per each snippet we create a file with the values of those columns or update the existing one with them as well. If the operation fails we retry only once.

Refs #39202 (closed)

Does this MR meet the acceptance criteria?

Conformity

• [ ] Changelog entry I don't think we need a CHANGELOG here since we will add it once we create the background migration that runs the code in this MR
• [ ] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content