Make tests that wait for concurrent work wait on the event or a condition with a long deadline (issue 1814)

A test that slept a fixed time and then asserted what a goroutine, process or
watcher did failed under the checker's load. Each now waits for its positive
evidence (a started baseline, a call counted, a state reached) within 30 s, and
the concurrency-limit tests meet at a barrier instead of overlapping by sleep.

Claude-Session: https://claude.ai/code/session_01NcbgfJ9Gum47zkFKWRaovL

modules/sensors/cmd/sensors/second_review_test.go

@@ -31,10 +31,10 @@ func TestAStuckReadIsUnhealthyAndDoesNotStopTheOtherDrives(t *testing.T) {
 		if err != nil {
 			t.Fatal(err)
 		}
-	case <-time.After(5 * time.Second):
+	case <-time.After(30 * time.Second):
 		t.Fatal("a look waited on a stuck drive")
 	}
-	deadline := time.Now().Add(5 * time.Second)
+	deadline := time.Now().Add(30 * time.Second)
 	for {
 		_ = w.write()
 		r, _ := m.ReadReadings(DrivesPath)