Introduce new module mount implementation

Rewrite the whole module mounting logic from scratch.
Even the algorithm is different compared to the old one.

This new design focuses on a few key points:
- Modular: Custom nodes can be injected into the mount tree.
  It's the main reason for starting the rewrite (needed for Android 11)
- Efficient: Compared to the existing implementation, this is the most
  efficient (both in terms of computation and memory usage) design I
  currently can come up with.
- Accurate: The old mounting logic relies on handling specifically every
  edge case I can think of. During this rewrite I actually found some
  cases that the old design does not handle properly. This new design is
  architected in a way (node types and its rankings) that it should
  handle edge cases all by itself when constructing mount trees.

native/jni/Android.mk

@@ -20,6 +20,7 @@ LOCAL_SRC_FILES := \
 	core/db.cpp \
 	core/scripting.cpp \
 	core/restorecon.cpp \
+	core/module.cpp \
 	magiskhide/magiskhide.cpp \
 	magiskhide/proc_monitor.cpp \
 	magiskhide/hide_utils.cpp \