refactor: pass experiment arguments using a struct (#983)

Closes https://github.com/ooni/probe/issues/2358.

internal/engine/experiment/tlstool/tlstool.go

@@ -78,12 +78,11 @@ var allMethods = []method{{
 }}
 
 // Run implements ExperimentMeasurer.Run.
-func (m Measurer) Run(
-	ctx context.Context,
-	sess model.ExperimentSession,
-	measurement *model.Measurement,
-	callbacks model.ExperimentCallbacks,
-) error {
+func (m Measurer) Run(ctx context.Context, args *model.ExperimentArgs) error {
+	callbacks := args.Callbacks
+	measurement := args.Measurement
+	sess := args.Session
+
 	// TODO(bassosimone): wondering whether this experiment should
 	// actually be merged with sniblocking instead?
 	tk := new(TestKeys)