ENH: Transition project configuration to `pyproject.toml`

[jhlegarreta]

Transition project configuration to pyproject.toml.

Used the setup-py-to-pyproject-toml.py script in the ITKModuleTemplate repository: https://github.com/InsightSoftwareConsortium/ITKModuleTemplate

as a starting base, then made manual changes as necessary.

Require itk == 5.4.* and bump the package to a new major version.

[jhlegarreta]

Depends on PR #24.