Support dynamic version generation, including from git tags and with git commit hashes

meson-python should provide a way to use the ``__version__`` attribute of a package as its version instead of using the version from meson.

EDIT: for an extended description of this feature request, see https://github.com/FFY00/meson-python/issues/159#issuecomment-1266576327

No files, tests, or entry points are named in the issue. Start with the extended description in the linked comment, then trace how meson-python currently obtains the project version. Done should include a defined way to use a package's __version__, git tags, and git commit hashes.

Written by the indexing model from the issue text.