Investigate if window functions need a change of ownership when rerelating and, if so, add code to do so

Related to https://github.com/canonical/postgresql-k8s-operator/issues/772

PR https://github.com/canonical/postgresql-k8s-operator/pull/773 adds logic to change the ownership of procedures and aggregates, but not for window functions. This issue is to investigate if ownership needs changing and add logic to the lib, if so.

Start by reviewing related issue 772 and PR 773, then inspect the existing lib logic for changing procedure and aggregate ownership. Determine from the PostgreSQL behavior whether window functions also require ownership changes when rerelating. Done means recording that determination and adding the corresponding library logic if required.

Written by the indexing model from the issue text.