Restore support for pkginfo 1.11

[jaraco]

For now, this approach retains the current behavior that an unrecognized metadata version will fail with an error.

This approach splits out the detection based on the version of pkginfo. Starting with pkginfo 1.11, it now properly detects when a metadata version is unrecognized and errors on that condition explicitly. For backward compatibility, until pkginfo 1.11 is the minimum, the check will still provide guidance to consider the metadata version when fields are missing.

Closes #1116

[jaraco]

Well, shoot. It seems that after allowing pkginfo 1.11, the type checks are failing. It seems that pkginfo.Distribution.name was str and now is str | None. Same for .version.

[woodruffw]

Random thought: is there a reason this can't constrain pkginfo ~= 1.11 in pyproject.toml? That would avoid the need for the run-time version check + some of the extra handling in this PR.

[jaraco]

Random thought: is there a reason this can't constrain pkginfo ~= 1.11 in pyproject.toml? That would avoid the need for the run-time version check + some of the extra handling in this PR.

My thought was that there are probably users still reliant on older versions, so it would be nice to have at least one release transition where users aren't forced to the newer version. I absolutely agree that after twine stabilizes, we might bump the dependency on pkginfo (and remove the compatibility logic). I coded it in such a way as to make it easy to remove the compatibility logic.

I also observed that there's already an open issue #1070 tracking the move to pkginfo 1.10, so that issue would need to be addressed first (or simultaneously) with the move to 1.11.