Add fetchMoreForQueryId safeguards

[doomsower]

This PR addresses #3466

There are safety checks for unmounted queries, but there are not checks for fetchMore. This PR adds them.

Checklist:

• If this PR is a new feature, please reference an issue where a consensus about the design was reached (not necessary for small changes)
• Make sure all of the significant new logic is covered by tests
• If this was a change that affects the external API used in GitHunt-React, update GitHunt-React and post a link to the PR in the discussion.

[hwillson]

Hi @doomsower - thanks for submitting this PR. There is a bit of overlap between your changes and the recently merged changes from #3367. I'll get things cleaned up a bit, and will have this merged in shortly. Thanks!

[hwillson]

Thanks for this PR @doomsower! Since I had already merged #3367, most of your changes have been superseded by that PR. I've adjusted the CHANGELOG a bit in this PR, added some extra tests, and removed the additional safeguard that was added in the markQueryError function. That safeguard wasn't really needed, since a similar check is already being done in markQueryResultClient, which markQueryError calls. We should be all set to get this merged - thanks again!