Watcher fix ActivateWatchTests (elastic#82157)

This commit attempts to fix a set of Watcher tests that can
fail due to unexpected execution of Watches after Watcher has been stopped.

The theory here is that a Watch can be queued but not fully executed
then Watcher is shutdown, the test does some clean up, then the
queued Watch finishes execution and causes some some additional cleanup
to fail.

The change here ensures that when Watcher is stopped from AbstractWatcherIntegrationTestCase
that it will also wait until there are no more current Watches executing.

closes elastic#66495

x-pack/plugin/watcher/src/internalClusterTest/java/org/elasticsearch/xpack/watcher/test/AbstractWatcherIntegrationTestCase.java

@@ -567,7 +567,8 @@ protected void ensureLicenseEnabled() throws Exception {
 
     protected void stopWatcher() throws Exception {
         assertBusy(() -> {
-            WatcherStatsResponse watcherStatsResponse = new WatcherStatsRequestBuilder(client()).get();
+
+            WatcherStatsResponse watcherStatsResponse = new WatcherStatsRequestBuilder(client()).setIncludeCurrentWatches(true).get();
             assertThat(watcherStatsResponse.hasFailures(), is(false));
             List<Tuple<String, WatcherState>> currentStatesFromStatsRequest = watcherStatsResponse.getNodes()
                 .stream()
@@ -580,7 +581,8 @@ protected void stopWatcher() throws Exception {
                 .collect(Collectors.toList());
             List<WatcherState> states = currentStatesFromStatsRequest.stream().map(Tuple::v2).collect(Collectors.toList());
 
-            logger.info("waiting to stop watcher, current states {}", currentStatesFromStatsRequest);
+            long currentWatches = watcherStatsResponse.getNodes().stream().mapToLong(n -> n.getSnapshots().size()).sum();
+            logger.info("waiting to stop watcher, current states {}, current watches [{}]", currentStatesFromStatsRequest, currentWatches);
 
             boolean isAllStateStarted = states.stream().allMatch(w -> w == WatcherState.STARTED);
             if (isAllStateStarted) {
@@ -594,7 +596,7 @@ protected void stopWatcher() throws Exception {
             }
 
             boolean isAllStateStopped = states.stream().allMatch(w -> w == WatcherState.STOPPED);
-            if (isAllStateStopped) {
+            if (isAllStateStopped && currentWatches == 0) {
                 return;
             }