options/path: move path utility functions to misc/path_utils

These utility functions have nothing to do with user and config dir/file.
Move them to a separate file.

meson.build

@@ -139,6 +139,7 @@ sources = files(
     'misc/language.c',
     'misc/natural_sort.c',
     'misc/node.c',
+    'misc/path_utils.c',
     'misc/random.c',
     'misc/rendezvous.c',
     'misc/thread_pool.c',