lib.strings: Dont create scopes for getName/getVersion

We can create the `parse` function in a scope one level up to avoid recomputing it every time.

lib/strings.nix

@@ -715,10 +715,10 @@ rec {
        getName pkgs.youtube-dl
        => "youtube-dl"
   */
-  getName = x:
-   let
+  getName = let
     parse = drv: (parseDrvName drv).name;
-   in if isString x
+  in x:
+    if isString x
     then parse x
     else x.pname or (parse x.name);
 
@@ -732,10 +732,10 @@ rec {
        getVersion pkgs.youtube-dl
        => "2016.01.01"
   */
-  getVersion = x:
-   let
+  getVersion = let
     parse = drv: (parseDrvName drv).version;
-   in if isString x
+  in x:
+    if isString x
     then parse x
     else x.version or (parse x.name);