add `From<GlobError> for io::Error` impl

The conversion I would suggest is:

impl From<GlobError> for io::Error {
    fn from(err: GobError) -> io::Error {
        io::Error::new(err.error.kind(), err)
    }
}

This will keep the "pretty context" so that glob errors keep printing as:

"attempting to read `{}` resulted in an error: {}",
self.path.display(),
self.error

Which is already very ergonomic.

I can do this if you OK it 😄

Benefits / Justification

The glob error is already essentially an io::Error with a bit of additional context. This will allow functions that return io::Error can use glob with ? directly which incurs (basically) no performance issues.

Start by locating GlobError and its existing error-formatting implementation, then compare it with the requested io::Error conversion in the issue. Verify that the conversion preserves the existing contextual message and that functions returning io::Error can use glob errors with ?. Confirm the relevant test suite passes.