Delete snippet repositories

What does this MR do?

This MR updates the existing Snippets::DestroyService to remove the repository along with the snippet record.

It also creates a Snippets::BulkDestroyService to allow deleting in bulk snippets when the project or user associated with the snippet is deleted. This service first tries to remove the snippet repositories and, if everything is ok, then destroy_all snippets records (yes, destroy_all and not delete_all see !22672 (comment 293888693)). If anything goes south, the service tries to rollback the snippet repositories already marked to be removed.

Refs #39515 (closed)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content