Add a new plugin / extension mechanism called a resource provider along with retrofitting VFS on top of it.

A resource provider provides a mechanism for MuJoCo to read from filesystems other than the OS filesystem or the Virtual File System (VFS).

PiperOrigin-RevId: 525394983
Change-Id: I077ff5a7e2e76806b48b6defb531280aadc8b169

introspect/codegen/generate_structs.py

@@ -41,6 +41,10 @@ _ANONYMOUS_KEY_PATTERN = re.compile(r'\d+:\d+(?=\))')
 _EXCLUDED = (
     'mjpPlugin',
     'mjpPlugin_',
+    'mjpResourceProvider',
+    'mjpResourceProvider_',
+    'mjResource',
+    'mjResource_',
 )