Enforce global file size limit

What does this MR do and why?

Enforce global file size limit

• Add file_size_limit_mb to plan_limits
• Add enforce_global_file_size_limit flag to raise errors when files over the limit are pushed

Contributes to: #421435 (closed)

Changelog: added

How to set up and validate locally

1. Enable the global_file_size_check feature flag
2. Enable the enforce_global_file_size_limit feature flag
3. Try to push a file larger than 100 MB to a project (e.g head -c 104857601 /dev/urandom > 100_mb_plus_1) The push should be prevented with an error message

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #421435 (closed)