Use threadctrl to avail of context cancellation but still rely on a w…

…ait group to blocl until the lookups finish

core/services/ocr2/plugins/ocr2keeper/evm21/streams_lookup.go

@@ -148,10 +148,14 @@ func (r *EvmRegistry) streamsLookup(ctx context.Context, checkResults []ocr2keep
 	}
 
 	var wg sync.WaitGroup
-	for i, lookup := range lookups {
-		wg.Add(1)
-		go r.doLookup(ctx, &wg, lookup, i, checkResults, lggr)
-	}
+	wg.Add(len(lookups))
+
+	r.threadCtrl.Go(func(ctx context.Context) {
+		for i, lookup := range lookups {
+			go r.doLookup(ctx, &wg, lookup, i, checkResults, lggr)
+		}
+	})
+
 	wg.Wait()
 
 	// don't surface error to plugin bc StreamsLookup process should be self-contained.