Parallelize matrix field broadcasting tests

[charleskawczynski]

Supersedes #1616. This should hopefully shine light on what's going on.

[charleskawczynski]

@dennisYatunin, I think I may have run into this in the past: move variables or a function definition from inside @testset to outside, and JET gives different results. IIRC, function definitions outside of @testset more closely match what you see in applications.

Maybe I'm missing something, but it may be that these passing JET tests are actually a false positive pass because too many things are inside @testset. There have been issues with JET not detecting issues (aviatesk/JET.jl#608).

I'll need to dig into this more to confirm.

[charleskawczynski]

Ahhh, the last build is not reaching the job that actually fails, so these inference tests are never reached. They're actually just failing on main. I'll make the 5 failing jobs soft fail, so that we at least hook in the tests that are being reached.

[charleskawczynski]

@dennisYatunin, I'm going to move forward with merging this, please let me know if you want to follow up with any changes.