Python Module: Bundle VFX library python bindings

When calling bpy.utils.expose_bundled_modules(), these modules are
added to sys.path.

This provides a solution/workaround to two problems:
* Using bpy together with packages like usd-core is problematic. Besides
  crashing due to C++ symbol conflicts, it's just impossible to import
  different versions of the same module, or to have distinct environment
  variables for both. (#127132)
* Blender add-ons using these VFX modules do not currently work with
  the bpy module.

This adds about 15MB to the bpy package.

Pull Request: https://projects.blender.org/blender/blender/pulls/133082

doc/python_api/examples/bpy.types.HydraRenderEngine.py

@@ -22,6 +22,9 @@ class CustomHydraRenderEngine(bpy.types.HydraRenderEngine):
     # Register path to plugin.
     @classmethod
     def register(cls):
+        # Make pxr module available, for running as bpy pip package.
+        bpy.utils.expose_bundled_modules()
+
         import pxr.Plug
         pxr.Plug.Registry().RegisterPlugins(['/path/to/plugin'])
 

doc/python_api/examples/bpy.types.USDHook.py

@@ -185,11 +185,15 @@ bl_info = {
 
 import bpy
 import bpy.types
+import textwrap
+
+# Make pxr module available, for running as bpy pip package.
+bpy.utils.expose_bundled_modules()
+
 import pxr.Gf as Gf
 import pxr.Sdf as Sdf
 import pxr.Usd as Usd
 import pxr.UsdShade as UsdShade
-import textwrap
 
 
 class USDHookExample(bpy.types.USDHook):