Implement PEP735 dependency groups and PEP804 external dependencies

[jhale]

https://peps.python.org/pep-0735/

"This PEP specifies a mechanism for storing package requirements in pyproject.toml files such that they are not included in any built distribution of the project."

This would allow us to move test, ci, lint and docs optional dependency groups to new dependency groups. This allows dependency groups to be installed independently from the package itself, which is useful for CI and building images.

Also of interest, but still in draft:

https://peps.python.org/pep-0804/

"This PEP specifies a name mapping mechanism that allows packaging tools to map external dependency identifiers (as introduced in PEP 725) to their counterparts in other package repositories."