Update snippet file count limit depending on Feature Flag

What does this MR do?

In this MR we introduce a new feature flag called snippet_multiple_files. This ff will gather all the new logic surrounding the multiple files functionality. In this MR we raise the snippet max file limit if the feature flag is enabled.

📣 This MR is behind a beta feature flag and we tracking the rollout in #217809 (closed).

Refs #211349 (closed)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• [-] Documentation (if required) behind feature flag
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content