Blend animation direct change

- silence a few linter issues
- update default blend animation mix value to be 100. its either 0 or 100, 1 made no sense. i think 100 is right.
- made a clamped input converter to set values between 0 & 100 nicely & it rounds values when you drag

adds option for selecting setting the mix input or the mix value on uat @alxgibsn, what do we want this to say? "Set Blend Value? "Set Mix Value?

<img width="320" alt="image" src="https://user-images.githubusercontent.com/1216025/229121083-d8233155-4bce-475e-bdb3-697ebd951360.png">

can have both by input and by value, they look very subtlely different
<img width="272" alt="image" src="https://user-images.githubusercontent.com/1216025/229121329-f8bd8596-0247-42f9-bd82-1979778b8ad3.png">

Diffs=
d9fc7d927 Blend animation direct change (#5080)

.rive_head

@@ -1 +1 @@
-6df791fe4cbf6f70dc026314400d88ce3fec0a79
+d9fc7d92736d3ac97fafc2f2713ec25211584799

lib/src/generated/animation/blend_animation_direct_base.dart

@@ -38,7 +38,7 @@ abstract class BlendAnimationDirectBase extends BlendAnimation {
 
   /// --------------------------------------------------------------------------
   /// MixValue field with key 297.
-  static const double mixValueInitialValue = 1;
+  static const double mixValueInitialValue = 100;
   double _mixValue = mixValueInitialValue;
   static const int mixValuePropertyKey = 297;