Move package metadata and tool configuration to pyproject.toml

[matt-graham]

Fixes #1126 and fixes #1156

Moves from setup.py / setup.cfg based approach of specifying package metadata and tool configuration to more modern pyproject.toml based approach.

This allows getting rid of various separate configuration / metadata files (.coveragerc, requirements/*.in, setup.cfg, setup.py) in favour having all configuration centralized in pyproject.toml.

This PR also removes the previous .bumpversion.cfg file in favour of moving to setuptools-scm to automatically set package version based on Git metadata / tags (default versioning scheme is described here).

The tox check environment is updated to use Ruff in place of flake8 as Ruff is a lot quicker and supports pyproject.toml which flake8 currently doesn't. For now to keep the changes minimal here, I've added a series of rules to ignore that cause the Ruff check to fail. In a separate PR we probably want to either move to adding specific # noqa: ... overrides at the relevant places if we think what we have in the code is correct or fix the violations.

I've also removed the previous requirements/Makefile in favour of adding a new requirements tox environment that updates the requirements files using pip-compile (with input requirements now sourced from dependencies specified in pyproject.toml, including optional dev dependencies). I've also regenerated the requirements files so that the commented sources / generation command align with new structure but as far as I can see from a quick check this hasn't led to any changes in resolved packages. (EDIT: Beyond a few changes from adding ruff to development dependencies).

EDIT: Now also adds pylint to checks, as for ruff disabling rules that currently cause checks to fail with intention of fixing actual violations in separate PRs and/or adding specific # noqa: ... overrides.

[tbhallett]

Thanks for this one @matt-graham. Just noting that this one is the critical one for the first release with the paper submission