fix(E2E): ensure miniooni.bash is WAI (#972)

This diff re-enables `E2E/miniooni.bash`. To make it working properly, we
needed to figure out which were the right cloudfronts to use.

I looked into the configuration and determined that both cloudfronts
should be used because they basically map to the same host.

I also determined it was backwards to test a mixture of prod and testing
APIs, and probably also flaky. So, I  choose to only test the prod.

Additionally, I added support for testing all supported tunnels.

Closes https://github.com/ooni/probe/issues/2336

internal/cmd/e2epostprocess/main.go

@@ -27,6 +27,7 @@ type Measurement struct {
 }
 
 func main() {
+	backend := flag.String("backend", "https://api.ooni.io/", "Backend to use")
 	expected := flag.Int("expected", 0, "Expected number of measurement files")
 	flag.Parse()
 	if *expected <= 0 {
@@ -61,6 +62,7 @@ func main() {
 			options := []string{
 				"run",
 				"./internal/cmd/apitool",
+				"-backend", *backend,
 				"-mode", "meta",
 				"-report-id", entry.ReportID,
 			}