Follow the runtime's watches through mesh-sdk's KeptState.Follow, not four loops of their own (issue 774)

mesh-provisioner, mesh-config, mesh-issues and mesh-healers each wrote a watch-again loop (`watched`). mesh-sdk
61b67d61 adds KeptState.Follow, which asks again with backoff and says each give-up, and its watches now answer a
change at once and run the handler beside the runtime (the provisioner's "names no watch of this bundle"). The four
modules use it; their loops are gone. Built and tested against the mesh-sdk group head through a go.work that is not
committed: their mesh-sdk pins move to that head with the group.

modules/mesh-issues/cmd/mesh-issues/main.go

@@ -132,14 +132,8 @@ func main() {
 // reads the bucket, and a write carries the issue it changes first, so no write reaches the log before its
 // issue's carry.
 func start(t *Tracker) {
-	for wait := 2 * time.Second; ; wait = min(wait*2, time.Minute) {
-		time.Sleep(wait)
-		if err := stdio.State(IssuesState).Watch("", t.Watched); err != nil {
-			logf("[mesh-issues] the bucket is not watched yet (%v); asking again in %s", err, wait)
-			continue
-		}
-		break
-	}
+	// Asked again until the runtime takes it, each give-up said (mesh-sdk's Follow).
+	stdio.State(IssuesState).Follow("", t.Watched)
 	for wait := 2 * time.Second; ; wait = min(wait*2, time.Minute) {
 		s, err := t.Start()
 		if err == nil {