move `remove-cache-prefix` to new `path.nu`

bins/inbreeding/load.nu

 use consts.nu
+use path.nu [ "remove-cache-prefix" ]
 use ../../.nushell error "error throw"
 
-def remove-cache-prefix []: path -> string {
-    str replace $"($consts.CACHE)(char path_sep)" ''
-}
-
 # return experiment names following `$ARG_EXPERIMENT_FORMAT`
 def get-experiments []: nothing -> list<string> {
     $consts.CACHE

bins/inbreeding/path.nu

+use consts.nu
+
+export def remove-cache-prefix []: path -> string {
+    str replace $"($consts.CACHE)(char path_sep)" ''
+}