Add the grpcnotrace build tag for hfc builds

This finally unlocks dead code elimination for the Lambda handler, which
takes the binary from ~31 MB to ~20 MB. That's a huge difference!

Author: featherbread

hfc.toml

@@ -3,6 +3,7 @@ name = "randomizer"
 
 [build]
 path = "./cmd/randomizer-lambda"
+tags = ["grpcnotrace"]  # note that lambda.norpc is implicit for all hfc builds
 
 [template]
 path = "CloudFormation.yaml"