Avoid using pouchdb-server in CI and local tests

[espy]

Destroying databases is flaky in pouchdb-server. This PR supersedes #9204

Overview

PouchDB integration tests were very flaky, with random timeouts. We (NH) identified this being caused by an issue with pouchdb-server, where the destroy() method used to clean up test DBs didn’t actually remove the test databases. The tests no longer seem to time out when using a CouchDB via COUCH_HOST instead of pouchdb-server. This PR changes the CI setup so we can verify this assumption by running the CI repeatedly.

We moved the node PERF tests out into their own nodejs-perf Job , since our changes conflicted with that particular bit of the node job.

In addition: updated TESTING.md to reflect that COUCH_HOST is basically mandatory at this point in time. Also removed references to Admin Party, added a ToC and made a bunch of other small improvements.

Testing recommendations

We want to re-run the test suite multiple times to se whether the timeouts are resolved, and if so, submit this as a fix.

Checklist

• I am not a bot
• This is my own work, I did not use AI, LLM's or similar technology for code or docs generation
• Code is written and works correctly
• Changes are covered by tests
• Documentation changes were made in the docs folder

[espy]

CI is now consistently green with these changes, but I can’t get that one pending check to resolve itself (nodejs (20, CLIENT=firefox npm run test-webpack). Re-opening the PR and starting a new branch with a new PR both did not work.

I assume the reason for this is that we changed one of the CI commands: CLIENT=firefox npm run test-webpack no longer exists, but GH seems to think it should. I hope this goes away after merging.