Revert stage 2 and 3 of SiteConfiguration/History field rename

1. Context
   The SiteConfiguration and SiteConfigurationHistory models had their `values` field renamed to `site_values` in a few PRs from #22692 to #22753. The testing plan has been defined in [Data Engineering docs](https://openedx.atlassian.net/wiki/spaces/DE/pages/1065681172/Patterns+For+Renaming+Django+Model+Fields#PatternsForRenamingDjangoModelFields-RolloutPlanForCreditRequirement.orderIntheLMS), however these docs don't mention that each stage should be performed in separate release to avoid downtime or altering business logic between releases, as defined in [Architecture and Engineering docs](https://openedx.atlassian.net/wiki/spaces/AC/pages/23003228/Everything+About+Database+Migrations#EverythingAboutDatabaseMigrations-Howtorenameacolumn).

This is a PoC PR that reverts stage 2 and 3 of #22753. The only conflict was in the `common/djangoapps/util/tests/test_db.py` file, so these reverts do not seem to be too invasive code-wise. Not sure about any other implications, though. It would be good to get some edX feedback here.

*Note:* This is missing the relevant migrations, so it won't work as-is. We would need to add back the reverted migrations and then create new migrations that would:
1. Bring back the removed `values` fields of `siteconfiguration` and `siteconfigurationhistory`.
1. Copy the contents of `site_values` fields into `values` fields.