Cleanup: remove duplicate context variable (__py_context)

The context was stored both in __py_context & bpy_context_module.

This avoids duplicate functions to update them too.

source/blender/python/BPY_extern_python.h

@@ -32,7 +32,7 @@ extern "C" {
 #include <stdio.h>
 
 /* bpy_interface.c */
-void BPY_python_start(int argc, const char **argv);
+void BPY_python_start(struct bContext *C, int argc, const char **argv);
 void BPY_python_end(void);
 void BPY_python_reset(struct bContext *C);
 void BPY_python_use_system_env(void);