Deprecate registry.database in favor of global.registry.psql

Summary

Comments from #5854 (comment 2379720549):

postgresql sub-Chart need to access the name/key of the registry database secret to provision the db.

So we need to migrate at least name, user and password to global

Success Criteria

• global.registry.psql has enabled, password, username and database (rename those fields to keep in line with other similar configurations)
• global.registry.psql takes precedence, with registry.database as fallback.
• (potentially) global.registry.psql.enabled defaults to true. This will need extra works to ensure not breaking existing instances.