Should we cache `Database::Connection.config` ?

1. Should we cache Database::Connection.config ? If not we can remove uncached_config
2. Otherwise we should make uncached_config private.

The following discussion from !66988 (merged) should be addressed:

• @ashmckenzie started a discussion: (+1 comment)

  question: One perhaps for a follow-up in the interest of getting this fix out, but could uncached_config be made private to discourage from public use?

/cc @yorickpeterse