proposal: use setuptools/setuptools_scm for building

[dtrifiro]

This PR changes the build system from flit to setuptools+setuptools_scm. The main driver behind this PR is to simplify development by having setuptools_scm automatically set the module version at build/install time instead of having a fixed 0.0.1 version replaced by CI.

Another advantage of using setuptools_scm is to have proper versions reported when using editable installs, avoiding version requirements warnings/errors.

This also adds the possibility of using caikit_nlp.__version__ (or __version_tuple__) to check the module version at runtime

[dtrifiro]

An example of what the version generated by setuptools-scm: 0.2.2.dev39+g8cfe9b8: it includes git tag, number of commits since last tag and the git ref for the build.

[dtrifiro]

Hey @gabe-l-hart, do you have any bandwidth to have a look at this and/or discuss it?

[gkumbhat]

I like this change. @gabe-l-hart or @evaline-ju or @joerunde thoughts on this? Also do we want to include this for caikit as well?

Currently caikit-nlp cannot be published to pypi itself because of peft version, but something seems this would be useful for caikit and once we are able to push caikit-nlp to pypi.

[dtrifiro]

I have a patch ready for caikit aswell if this is approved.

[joerunde]

@dtrifiro yeah this looks better than what we whipped up when we pulled this all out into github. Thanks!

Can you go ahead and make the change to caikit as well?

[joerunde]

Ah, I am not a code owner here so I'd actually need @gkumbhat to hit approve on this PR

[gabe-l-hart]

Looks good. Thank you!

[dtrifiro]

This PR had a small issue which was fixed in #239, see pypa/setuptools#3340 for more context.