feat(miniooni): run local oonirun v2 descriptor (#966)

We introduce the -f, --input-file FILE option with which we
are able to run an OONI Run v2 descriptor stored locally.

In this running mode, there are no checks related to whether the
descriptor has changed, since we're dealing with a local file.

Closes https://github.com/ooni/probe/issues/2328

internal/cmd/miniooni/main.go

@@ -196,6 +196,13 @@ func registerOONIRun(rootCmd *cobra.Command, globalOptions *Options) {
 		[]string{},
 		"URL of the OONI Run v2 descriptor to run (may be specified multiple times)",
 	)
+	flags.StringSliceVarP(
+		&globalOptions.InputFilePaths,
+		"input-file",
+		"f",
+		[]string{},
+		"Path to the OONI Run v2 descriptor to run (may be specified multiple times)",
+	)
 }
 
 // registerAllExperiments registers a subcommand for each experiment