Workspace renaming: Interpret outputs as nondirectional

Currently when renaming outputs, an output assignment of "left" will
cause the workspace to move left. Treat this assignment as a proper name
instead (even though it is unlikely an output will be named "left").

Move logic for determining output to move to out of
`workspace_move_to_output`

Add test for ignoring direcionality during rename.

Fixes #3208.

include/workspace.h

@@ -207,4 +207,4 @@ Con *workspace_encapsulate(Con *ws);
  * This returns true if and only if moving the workspace was successful.
  *
  */
-bool workspace_move_to_output(Con *ws, const char *output);
+bool workspace_move_to_output(Con *ws, Output *output);