Remove stopped queries from store and internal tracking

[helfer]

Fixes #902 #903 (?) #993 #1026

This was a pretty hairy affair, but I think I've managed to untangle things enough so that stopped queries are now actually removed from the store and no longer tracked. That means that their reducers and updateQuery functions no longer run.

I don't think #903 is really fixed by this, but the discussion there is so long that I think it's better if we start a new issue about running reducers for other variables than the current query variables (cc @richburdon @yurigenin)

TODO:

• If this PR is a new feature, 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
• Rebase your changes on master so that they can be merged easily
• Make sure all tests and linter rules pass
• Update CHANGELOG.md with your change
• Add your name and email to the AUTHORS file (optional)
• If this was a change that affects the external API, update the docs and post a link to the PR in the discussion