fix(Runtime): Don't check for animator initialized state in constraints

Summary:
Checking for `isInitialized` on Animator caused the animator to not be used by constraints, since a constraint might initialize before the Animator has a chance to. It should be fine to access an animator's bone transforms before initialization.

I've accessed bone transforms like the Hip on an un-initialized Animator and the Animator still returns a valid reference.

Reviewed By: tseglevskiy

Differential Revision: D46580909

fbshipit-source-id: ea20f616d296adc1c9a24eee47b860056ad7a713

Author: sohailshafiiWk

Runtime/Scripts/AnimationRigging/DeformationConstraint.cs

@@ -344,15 +344,15 @@ private bool SkeletonOrAnimatorValid()
         {
             return
                 (_customSkeleton != null && _customSkeleton.IsInitialized) ||
-                (_animator != null && _animator.isInitialized) ||
+                (_animator != null) ||
                 (_skeleton != null && _skeleton.IsInitialized);
         }
 
         /// <inheritdoc />
         public bool IsBoneTransformsDataValid()
         {
             return (_customSkeleton != null && _customSkeleton.IsDataValid) ||
-                (_animator != null && _animator.isInitialized) ||
+                (_animator != null) ||
                 (_skeleton != null && _skeleton.IsDataValid);
         }
 

Runtime/Scripts/AnimationRigging/GroundingConstraint.cs

@@ -416,7 +416,7 @@ public void SetDefaultValues()
         public bool IsBoneTransformsDataValid()
         {
             return (_skeleton != null && _skeleton.IsDataValid) ||
-                (_animator != null && _animator.isInitialized);
+                (_animator != null);
         }
     }
 

Runtime/Scripts/AnimationRigging/TwistDistributionConstraint.cs

@@ -277,7 +277,7 @@ private static Vector3 Convert(Axis axis, bool inverted)
         public bool IsBoneTransformsDataValid()
         {
             return (_skeleton != null && _skeleton.IsDataValid) ||
-                (_animator != null && _animator.isInitialized);
+                (_animator != null);
         }
 
         bool IAnimationJobData.IsValid()