Elasticsearch: Add Moving Function Pipeline Aggregation (#28131)

* Elasticsearch: Add Moving Function Pipeline Aggregation

* Removing support for moving average in 7.x

* Fixing getMetricAggTypes to handle undefined esVersion

* Adding moving_fn to go code

* Update public/app/plugins/datasource/elasticsearch/metric_agg.ts

Co-authored-by: Giordano Ricci <grdnricci@gmail.com>

* Adding test for esversion 70

* Removing default value for script, adding placeholder instead

* Fixing formatting

* Adding code for handling missing or obsolete aggregations

Co-authored-by: Giordano Ricci <grdnricci@gmail.com>

pkg/tsdb/elasticsearch/models.go

@@ -45,6 +45,7 @@ var metricAggType = map[string]string{
 	"percentiles":    "Percentiles",
 	"cardinality":    "Unique Count",
 	"moving_avg":     "Moving Average",
+	"moving_fn":      "Moving Function",
 	"cumulative_sum": "Cumulative Sum",
 	"derivative":     "Derivative",
 	"bucket_script":  "Bucket Script",
@@ -64,6 +65,7 @@ var extendedStats = map[string]string{
 
 var pipelineAggType = map[string]string{
 	"moving_avg":     "moving_avg",
+	"moving_fn":      "moving_fn",
 	"cumulative_sum": "cumulative_sum",
 	"derivative":     "derivative",
 	"bucket_script":  "bucket_script",