## Summary
Watch plugins now are checked for key conflicts…
- Some built-in keys remain overridable (specificically `t` and `p`).
- Any key registered by a third-party watch plugin cannot be overridden by one listed later in the plugins list config.
Fixes#6693.
Refs #6473.
## Test plan
Additional tests are provided that check every conflict / overwritable scenario discussed.
## Request for feedback / “spec” evolution
The “spec” is an ongoing discussion in #6693 — in particular, the overwritability of some built-in keys, such as `a`, `f` and `o`, may be subject to discussion. This PR tracks the decisions in there and may evolve a bit still.
Ping @SimenB @thymikee @rogeliog for review and discussion.
* Allow WatchPlugins access to a broader list of global config options
Refs #6467
* Tests for whitelisting config options in WatchPlugins
* Docs on allowed config options in WatchPlugins
* chore: Changelog
* tests: leverage it.each to clean up code
* refactor: centralize config update logic
* Update plugin test to use new signature for configs
* Refactor watch extensions as per PR review (#6473)