Introduce mjPreContact, a minimal struct passed into the collision functions.

PiperOrigin-RevId: 918533795
Change-Id: I2b5af05c1479b25d5c2cfdc690321a26fce6ede6

python/mujoco/raw.h

@@ -25,6 +25,7 @@
 // to them under the "raw" namespace.
 namespace mujoco::raw {
 
+using MjPreContact = ::mjPreContact;
 using MjContact = ::mjContact;
 using MjData = ::mjData;
 using MjLROpt = ::mjLROpt;