[ci] Move static tests into separate job

[eps1lon]

Two longest jobs currently are test_unit and test_build. These have some steps that are don't depend on previous steps and therefore can be safely extract.

New job is called test_static which describes the steps good enough (format, lint, types, docs generation). Every (custom) step in this job could potentially run parallel to the other steps.

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[oliviertassinari]

We only have 5 concurrent jobs available with Circle CI. Running 5 jobs means that a single pull request takes all the resource. Could that have a negative impact?

[eps1lon]

We only have 5 concurrent jobs available with Circle CI. Running 5 jobs means that a single pull request takes all the resource. Could that have a negative impact?

If we have 5 jobs available and this change doesn't go over the limit I don't see how this could cause any issues? If our builds can run in parallel then we were already starved anyway.

[oliviertassinari]

I was wondering if we would lose global throughput (because each test as a compressive yarn install setup, 5 yarn install is slower than 4), but even if we do, I agree with the approach, the feedback loop for the tests is very important, the shorter they are (for a given one), the more productive we can be 👍.

[eps1lon]

Sure it's not guarenteed that this will helps since I can't simulate heavy load on the CI environment. This is technically the better approach. We have to monitor how this works out (just like any other change).

If yarn install becomes the bottleneck we can scale the machine power. Just restoring cache already takes 30s which is quite long. Rrestoring node_modules/ might be the better approach. Another bottleneck might be compiling of pupeteer since it doesn't come with pre-built binaries.