[ML] Add .reindexed-v7-ml-anomalies-* to anomaly results template index pattern (elastic#135270)

Anomaly detection results indices created in a version 6 Elasticsearch
are reindexed and renamed with the ".reindexed-v7" prefix in version 7. 
In 8.18 and 8.19, those version 7 indices are rolled over in preparation 
for the version 9 upgrade. ".reindexed-v7-ml-anomalies-*" is
added to the AD results index template index patterns so when those
indices are rolled over the pick up the correct mappings

Author: davidkyle

docs/changelog/135270.yaml

@@ -0,0 +1,5 @@
+pr: 135270
+summary: Add .reindexed-v7-ml-anomalies-* to anomaly results template index pattern
+area: Machine Learning
+type: bug
+issues: []

x-pack/plugin/core/template-resources/src/main/resources/ml/anomalydetection/results_index_template.json

@@ -2,7 +2,7 @@
   "priority": 2147483647,
   "version" : ${xpack.ml.version.id},
   "index_patterns" : [
-    ".ml-anomalies-*"
+    ".ml-anomalies-*", ".reindexed-v7-ml-anomalies-*"
   ],
   "template" : {
     "settings" : {