fix: remaining issues in the test suite following the upgrade to kokkos-5.1

[svalat]

This PR contains several fixes to make the test suite passing again after the upgrade to kokkos-5.1 :

1. Removal of a non required volatile keyword in an operator+=
2. add pybind11 to test/python_requirements.txt as it is used by some tests
3. add a python package pre-install action to build a venv before running the tests suite in github actions
4. Finish to rename some types HostMirror => host_mirror_type

The test suite is now passing again.

[neutrinoceros]

This comment makes the one I added to inifix redundant.

While this is being looked at, could we specify a minimal requirement for Python itself, even if it's just a comment ?

3.11 is widely distributed and likely sufficient nowadays, if I may add a suggestion.

[glesur]

I'm assuming you're refereing to #381 ? I don't see how this comment make yours redundant,nor why we should require python 3.11 (this is only 4 years old)

[neutrinoceros]

no I'm talking about the comment on line 9 of the same file. It doesn't matter any more that inifix requires 3.6+ if another dependency requires an even newer version.

(this is only 4 years old)

Python versions stop receiving security fixes after 5 years, and 3.10 is about to go EOL. That's why I don't recommend older versions. But of course you do you.
https://devguide.python.org/versions/