Remove onBackPressed() usage [1/x]

[cketti]

A first step in removing custom onBackPressed() implementations and calls to this method.

See #6476

[wmontwe]

LGTM

I just wondered about this and the following pull-requests that there are super tiny commits that logically could be in one step, especially as there was previously a demand to keep the commit count low because of git history.

[cketti]

While there's the common goal of removing usages of onBackPressed(), each commit uses a slightly different approach (hopefully) appropriate for the context. Separating the changes makes it easier to change the approach in a particular case should the reviewer suggest a better alternative. I think it also makes it easier to review the code.

In general I think having granular commits is a good thing. What I think we can and should avoid is having unnecessary fixup commits. Fixup commits are nice during code reviews, but should be squashed before a PR branch is merged. Fixup commits are unnecessary noise once the review is done.