Refac test implementation

[szabo137]

With this PR, I propose a major refactoring of the test implementation, mostly to drop QEDcore.jl as a test dependency. See #144 for details.

TODO (unit tests itself)

• particle: check only particle properties
• particle: implement and check propagator
• particle: implement and check base_state
• process: moving parts that do not belong to processes (marked in the code by TODO)
• particle stateful: implement some tests
• cross section: remove coordinate-based evaluation (is checked in PSP tests)
• core_compat: move to QEDcore.jl

TODO (test implementation)

• psp: make TestPhaseSpacePoint(...,moms) type-stable
• psp: implement proper in- and out-psps
• particle: implement massless particles
• psl: implement failing PSL

TODO (general)

• consider testing everything for (TestMomentum{T}, TestMomentumMutable{T}) where T<:Union{Float16,Float32, Float64} (not just for TestMomentum{Float64})

Final remarks

Solves #144.

Makes #140 easier to achive.

[szabo137]

@AntonReinhard This one is almost done. I have a fix for the GPU tests, which I tested for CUDA, and I will push if I tested it locally for AMDGPU as well.

I think most of the rest could be reviewed. Sorry for the long list of changes, but most of it is reshuffling and renaming of things.

Btw: I expect no comment earlier than mid January 😉

[AntonReinhard]

Very nice, removing the circular dependency will definitely help the future development.
I've looked through more or less on surface-level since it's kind of a lot 😅

[szabo137]

Thanks for the rapid reply. I changed the code accordingly.

[szabo137]

@AntonReinhard how do we proceed with this one? From my side, it looks like final. But feel free to add more comments 😊

[AntonReinhard]

LGTM
What about the one last unchecked box in the PR description?