fix: weighted layer support in NetworkAnimator MTT-2698

[mattwalsh-unity]

NetworkAnimator previously lacked 2 things:

• it only looked at the primary layer (0)
• it did not sync runtime-adjusted layer weights

This meant users with multiple layers had partial success at best. In this update all active layers of an animator are scanned and synchronized. Also, the weight setting for each layer is detected and forwarded.

MTT-2698

• Includes integration tests.
• We need to document that this feature is available. But no changes are required from the user to continue use this feature