UI for weighted repository storages

UI form to support saving repository storages as a weighted number.

as part of #39111 (closed), we need to modify the admin settings page so that instead of checkboxes for the repository storages, each repository storage can take a value between 0 - 100. This will use !31645 (merged) on the backend.

We also need to create a migration to seed data for repository_storages_weighted from repository_storages, where every value in repository_storages gets a value of 100 in repository_storages_weighted.

This migration can also remove the repository_storage, and we can remove methods associated with repository_storage as well.