Test other UNC-like prefixes besides \\?\

The test cases added in this commit are not very high value, since
any `\` in what is supposed to be a component should be detected as
invalid on Windows, which entails that these paths are detected as
such. Adding these is mainly to clarify that the `\\?\` is not
special here, comparedd to other kinds of `\` and `\\` paths.

Author: EliahKagan

gix-validate/tests/path/mod.rs

@@ -266,7 +266,10 @@ mod component {
             Error::WindowsPathPrefix,
             ALL_OPTS
         );
+        mktest!(unc_net_path, br"\\host", Error::PathSeparator, ALL_OPTS);
         mktest!(unc_path, br"\\?\pictures", Error::PathSeparator, ALL_OPTS);
+        mktest!(unc_device_path, br"\\.\pictures", Error::PathSeparator, ALL_OPTS);
+        mktest!(unc_nt_obj_path, br"\??\pictures", Error::PathSeparator, ALL_OPTS);
 
         #[test]
         fn ntfs_gitmodules() {