Update package management and update polars

[paulf81]

This pull request is a little bit of a hodge-podge but I hope helps address a few open issues.

Feature or improvement description

Following examples such as:

https://packaging.python.org/en/latest/guides/modernize-setup-py-project/

The process of migrating from setup.py to pyproject.toml is started. I think this process will help with:

• Based on above packaging link I think this is modern preference
• Issue [BUG] poetry version solving fails with floris and flasc #200 because I think poetry is more pyproject.toml based (@aclerc agree)?
• Opens possibility for using newer package managers directly (such as https://github.com/astral-sh/uv)
• Issue [BUG] Polars versioning #133 , in that I am maybe mixing issues, but was easier now to build directly into my .venv an environment that seems to have resolved ARM-related issues and all tests pass.
• An alternative here would be updating to the ARM/conda locally, but that's my problem, this works at least
• I think will also clarify in the future which python versions we're supporting more clearly

Also now updated versioning to focus into pyproject.toml, believe this follows modern standard:
https://packaging.python.org/en/latest/guides/writing-pyproject-toml/#writing-pyproject-toml
https://packaging.python.org/en/latest/discussions/single-source-version/#single-source-version

Some things to futher consider:

• Should confirm that normal pip install works with new configuration
  • Confirmed using CI
• Believe that setup.py (see packaging link) can become very minimal so we don't need to maintain two sets of information
  • Deleted setup.py, seems fine
• One mystery, I don't think pyproject.toml supports the long_description_content_type tag we added to setup.py in Add markdown flag #191 , so want to be sure we don't reignite pypi issues as in [BUG] PyPI update not working #190
  • I think based on: long_description vs. pyproject.toml pypa/packaging.python.org#1535, this is handled by specifying the README and not a seperate long_description