only run pip check once for Python installation + move det_installed_python_packages, det_pip_version, run_pip_check to Python easyblock

[boegel]

follow-up for #3432

The changes there don't apply to Python itself, since that doesn't use PythonBundle at all (which we can't do, because we import stuff from pythonpackage in there, which in turn imports stuff from the Python easyblock).

The det_installed_python_packages, det_pip_version, and run_pip_check function were moved (without any changes) to the Python easyblock, otherwise we can't use run_pip_check (since we can't import it from PythonPackage easyblock without introducing a cyclic import).

No changes are needed for easyblock that import for example det_pip_version (which was introduced a long time ago, in EasyBuild v4.1.0) from easybuild.easyblocks.generic.pythonpackage, that'll still work fine.

[boegel]

Test report by @boegel

Overview of tested easyconfigs (in order)

• SUCCESS Python-3.10.8-GCCcore-12.2.0.eb
• SUCCESS Python-bundle-PyPI-2024.06-GCCcore-13.3.0.eb
• SUCCESS matplotlib-3.9.2-gfbf-2024a.eb
• SUCCESS numexpr-2.9.0-foss-2023a.eb

Build succeeded for 4 out of 4 (4 easyconfigs in total)
node3502.doduo.os - Linux RHEL 9.4, x86_64, AMD EPYC 7552 48-Core Processor (zen2), Python 3.9.18
See https://gist.github.com/boegel/6c290c092e827687e1b0da33cc578b78 for a full test report.

[lexming]

LGTM

[lexming]

Merging, thanks @boegel !