[Scons] Implement module dependency sorting.

Modules can now call:

env.module_add_dependencies(name: str, deps: list, optional: bool)

To add required or optional dependencies during the "can_build" step.

Required dependencies will be checked and the module will be not be
enabled when they are missing, printing a warning to notify the user.

modules/gdscript/config.py

@@ -1,4 +1,5 @@
 def can_build(env, platform):
+    env.module_add_dependencies("gdscript", ["jsonrpc", "websocket"], True)
     return True