[PyROOT] Integrate JsMVA into PyROOT

[guitargeek]

There is no reason to not have JsMVA as a submodule of ROOT, but it would clearly simplify things.

In particular, this would simplify the life of packagers. Right now, ROOT creates several separate directories in site-packages, which prompts e.g. the Fedora guys to create separate packages for each of them: https://packages.fedoraproject.org/pkgs/root/

I think a python3-jsmva package is clearly an overkill, and with this commit we can change the situation (the package name doesn't even contain root, so how would one even know where it comes from).

Another benefit of this change is that the JsMVA Python sources are now correctly tracked by CMake, so they are re-copied of you update them in the source directory.

The python sources are re-formatted on this occasion.

[github-actions[bot]]

Test Results

    10 files      10 suites   1d 17h 53m 24s :stopwatch:  2 594 tests  2 594 :white_check_mark: 0 :zzz: 0 :x: 24 565 runs  24 565 :white_check_mark: 0 :zzz: 0 :x:

Results for commit 9417bb45.

[guitargeek]

Thanks! That should not be a problem. The python*-jsmva package will just be gone and the code is absorbed by python*-root.