Fix handling of maximum Python version in pick_python_cmd function in PythonPackage easyblock + require that maximum major Python version is specified if maximum minor Python version is specified

[Flamefire]

When the minor version is unset, only the major version must be checked.
Otherwise patch versions etc. must be ignored.
This allows:
3.7.4 for "max_py_majver=3" and "max_py_majver=3 max_py_minver=7"

However I'd argue that our current approach with max_py_maj/minver and req_py_maj/minver is error-prone anyway: It does not make sense to only specify a minor version for either. Hence I'd change that easyconfig parameter into a single one: required_python_version which is a string like "3.7", same for the max version.
This can then be converted to a LooseVersion and fully avoids the possibility of missing major versions as well as having only a single parameter instead of 2. We can convert the current parameters to the new one automatically and deprecate them for 5.1 or IMO better just remove them for 5.0 as currently ReFrame is the only EC using this and it is trivial to update.

• Requires run pip check only once for PythonBundle #3432

[boegel]

@Flamefire I changed to target branch in this PR from 5.0.x to develop, you should synchronize your PR branch with current develop branch (which has received a massive update after the release of EasyBuild v5.0.0, see #3670)

[boegel]

@Flamefire Can you sync this with develop now that #3432 is merged?

[Flamefire]

Rebased which removes the commits contained by the merged PR

[boegel]

Test report by @boegel

Overview of tested easyconfigs (in order)

• SUCCESS matplotlib-3.9.2-gfbf-2024a.eb
• SUCCESS numexpr-2.9.0-foss-2023a.eb

Build succeeded for 2 out of 2 (2 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/25f87d5b01e0ee6d082146b4d2dad216 for a full test report.

[boegel]

lgtm

[boegel]

Test report by @boegel

Overview of tested easyconfigs (in order)

• SUCCESS ReFrame-3.0.eb
• SUCCESS ReFrame-3.11.2.eb
• SUCCESS ReFrame-3.12.0.eb
• SUCCESS ReFrame-3.2.eb
• SUCCESS ReFrame-4.0.1.eb
• SUCCESS ReFrame-4.0.5.eb
• SUCCESS ReFrame-4.2.0.eb
• SUCCESS ReFrame-4.3.2.eb
• SUCCESS ReFrame-4.3.3.eb
• SUCCESS ReFrame-4.6.2-GCCcore-12.3.0.eb
• SUCCESS ReFrame-4.6.2-GCCcore-13.2.0.eb
• SUCCESS ReFrame-4.6.2.eb
• SUCCESS ReFrame-4.6.2-Python-3.6.eb
• SUCCESS ReFrame-4.6.3-GCCcore-13.3.0.eb
• SUCCESS ReFrame-4.7.4-GCCcore-13.2.0.eb
• SUCCESS ReFrame-4.7.4-GCCcore-13.3.0.eb
• SUCCESS ReFrame-4.7.4.eb
• SUCCESS ReFrame-4.7.4-Python-3.6.eb

Build succeeded for 18 out of 18 (18 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/0c1eea45ab104b4c46875a7923c65108 for a full test report.

[Flamefire]

Any thoughts about the proposal? I.e. changing:

- def find_python_cmd(log, req_py_majver, req_py_minver, max_py_majver, max_py_minver, required):
+ def find_python_cmd(log, req_version, max_version):  # Or min_version for req_version

-def pick_python_cmd(req_maj_ver=None, req_min_ver=None, max_py_majver=None, max_py_minver=None):
+def pick_python_cmd(req_version=None, max_version=None):

Usage would then change:

-        self.assertIsNotNone(pick_python_cmd(3, 6))
+        self.assertIsNotNone(pick_python_cmd('3.6'))
-        self.assertIsNotNone(pick_python_cmd(2, 6, 123, 456))
+        self.assertIsNotNone(pick_python_cmd('2.6', '123.456'))

We could keep a deprecation period as the new argument would be strings. A bit harder if we want to support the old keywords, but doable.