feat: add from_err() method to Report

[johnbchron]

There's no nice way to construct a bare Report from a regular Error type. You can construct Result<_, Report> from Result::<_, E: ...>, but not from an error by itself.

My workaround where e: impl Error + Send + Sync + 'static is to do Err::<(), _>(e).into_diagnostic().unwrap_err(), which obviously is ugly.

I added a Report::from_err() method that solves this problem in the same way as the IntoDiagnostic trait, by using its DiagnosticError type.

[zkat]

hey this is nice. Thanks!