Initial roll-out was for mediawiki/core.

Fresnel itself was written to remain standalone with this expansion in mind. It won't need any changes for this task.

The CI logic is where the dots are connected, and this is currently in place for mediawiki/core. I've written the Jenkins job config and Dockerfile with this use in mind, but it might not work for extensions as-is.

• Try to do it as-is.
• Fix stuff as needed.
• Run via "check perf" only at first.
• Add the patchset trigger for 1 extension repo (e.g. NavigationTiming).

Additional triggers can then be requested via their own task, or by submitting a patch to integration/config that adds the Fresnel job under the repo's section in zuul/layout.yaml.