Add an extensible generic check method for evaluating updates to an existing field

[everettraven]

This builds on top of #661 and if it is not already handled by the implementation in #661, focuses on adding a new check for updates to existing fields that is easily extensible. If no validation exists to handle the change to the existing field this check should fail

If the proposal for adding this functionality to carvel-dev/kapp has been accepted prior to starting this work, all changes should be made against carvel-dev/kapp, otherwise the changes should be made against https://github.com/everettraven/kapp/tree/feature/crd-upgrade-safety-preflight

[everettraven]

Done as part of carvel-dev/kapp#921 - closing