Filter out anonymous classes during test discovery

[lihaoyi]

Mitigates #3910 by hackily filtering out all anonymous classes, but non-anonymous non-test classes still cause the problem

Added a unit test to check this specific misbehavior

[lefou]

Since we're more or less just reusing the JupiterFramework, we should first check upstream, whether these spurious discovered test classes are incidentally or not. TBH, I have no idea of the complete feature set of Junit5.

Is there already an upstream issue we can link to?

[lefou]

It would be nice to also update to the latest version of jupiter-interface. Maybe this is already fixed upstream?

• Update jupiter-interface from 0.11.4 to 0.13.0 #3501

[lihaoyi]

@lefou oh thsts a good point, should take another look at that pr

[lihaoyi]

merging this first just as a mitigation. The upstream sbt-jupiter integrstion does do some special stuff beyond just being a test framework, so likely we need to see what its doing and replicate that logic in Mill

[lefou]

I'm going to cut a snapshot release, as I have a project where we have lots of these spurious zero-ran test runs. This is also a nice test for the new publish pipeline (#3904).