Add confidence flag to TargetEstimate

Sigmoid function used to convert a final cost to a confidence from 0-1.

Signed-off-by: Milind Upadhyay <milind.upadhyay@gmail.com>
Change-Id: Ia71b8542c4f14a2a6678b68f0aff3cff41e65f8c
diff --git a/y2022/vision/target_estimate.fbs b/y2022/vision/target_estimate.fbs
index f7dc93a..42a012d 100644
--- a/y2022/vision/target_estimate.fbs
+++ b/y2022/vision/target_estimate.fbs
@@ -52,6 +52,9 @@
   angle_to_camera:double (id: 3);
   // Rotation of the camera in the hub's reference frame
   rotation_camera_hub:Rotation (id: 4);
+  // Confidence in the estimate from 0 to 1, based on the final solver cost.
+  // Good estimates currently have confidences of around 0.9 or greater.
+  confidence:double (id: 7);
 
   blob_result:BlobResultFbs (id: 2);