Give every module the announcement test, on an exported test bus (issue 1790, S11, ADR 0495 §5)

announcetest.Check starts the module against a bus of the test's own and holds its
announcement equal to what its code declares; testbus leaves internal/ so a module's
own integration tests can start it.

go/process/conn_integration_test.go

@@ -22,7 +22,7 @@ import (
 )
 
 // selfSignedServer is a nats-server with JetStream and TLS, self-signed, for this test alone (mirroring
-// go/internal/testbus.Start, with a certificate added since testbus has none): a mesh's bus presents its own
+// go/testbus.Start, with a certificate added since testbus has none): a mesh's bus presents its own
 // certificate in no public trust store, which is exactly what a process pins to (ADR 0436 clause 4).
 func selfSignedServer(t *testing.T) (url, fingerprint string) {
 	t.Helper()