Save repository storages in application settings with weights

What does this MR do?

The goal is to allow an admin to input a number between 0 and 100 into the repository storages pane in application settings. This is meant to replace the current functionality which just saves repositories into an array. The first step is to create a new jsonb column that can be used to represent a weight for each storage.

• adds a repository_storages_weighted column to the application_setting table
• save repository storages on the repository storage page to save storages as a number

part of: #39111 (closed)

note: this MR doesn't include any UI changes

Screenshots

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

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team