PoC: update `PythonPackage` easyblock to build wheel first when installing Python package with `pip`

[Flamefire]

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(created using eb --new-pr)

This is a Proof of Concept only.

It adds the option to set use_pip = 'wheel' which matches more our build-test-install cycle.

Currently when using pip we have this:

• build step does nothing
• test step installs into a temporary directory with pip install --prefix /tmp/foo .
• install step installs to the final location with pip install --prefix /final/foo .

Confusingly all build options need to be passed to (pre)installopts and as Python usually creates a "wheel file" (basically a compiled, installable zip) this duplicates work.

This option when set does the following:

• build step: pip wheel --wheel-dir /new-tmp-dir
• test step installs into a temporary directory with pip install --prefix /tmp/foo /new-tmp-dir/*.whl
• install step installs to the final location with pip install --prefix /final/foo /new-tmp-dir/*.whl

This avoids duplicate work and ensures that what is tested is what gets installed (currently we build twice which could yield different results). It is also nice to have separate timing and output for the actual build

However it turned out a bit more involved than anticipated. E.g. not all options for pip install apply to pip wheel and vice versa. Also the time savings are not that great. I tested PyTorch 2.1.2 on a (admittedly high-cpu) machine. And after an initial build/install the times are:

• setup.py install: ~35s
• pip install .: ~63s
• pip install *.whl: ~17s

So the time saving is around 11s which IMO isn't worth the added complexity.
However it brings back a dedicated build step, which shows up as such in EB status/progress and not confusingly in the test or install step.