Reduce list of root files projectile searches for

And define them on a per-module basis. This reduces the number of file
checks it performs, particularly for non-project files.

Might help #1317

modules/lang/python/config.el

@@ -8,6 +8,9 @@ called.")
   "CLI arguments to initialize 'jupiter console %s' with when
 `+python/open-ipython-repl' is called.")
 
+(after! projectile
+  (pushnew! projectile-project-root-files "setup.py" "requirements.txt"))
+
 
 ;;
 ;; Packages