Rename the project to setuptools-scm

[jaraco]

As I pointed out in this message, it seems that this project is unclear on what its name is. Historically, the name has been setuptools_scm, but with the 8.0 release and the move to pyproject.toml, the project renamed to setuptools-scm, but kept the name setuptools_scm in other places.

Incidentally, the project also seems to have had setuptools-scm as the indicated name (pre-normalized) in the wheels for versions prior to 8.0 as well. It'd be interesting to know why that is.

I'm not particularly interested in what the name of the project is, but I am interested in being consistent about it and avoiding being capriciously inconsistent just because the normalization allows it.

[RonnyPfannschmidt]

lets migrate names to the normalized name for consistency for all paces where its not a import name or entry-point name

[jaraco]

lets migrate names to the normalized name for consistency for all paces where its not a import name or entry-point name

I'll leave [tool.setuptools_scm] alone for now, too. We can maybe take advantage of the name mismatch to utilize [tool.setuptools-scm] for a different purpose (as a section heading without implying behavior).