Es 7 12 (#366)

* wip for 7.11 deprecations

* Fix build errors for 7.11

* add public visibility to test templates

* keeping threadpool over executor for now

* remove all the checks except keep nebula disabled

* Restore override annotation in TransportAddFeatureToSet

* read() was removed

* Bring back checkstyle and fix some violations

* Clean up unused vars

* 7.12 changes

* ES 7.12.1

Co-authored-by: Nathan Day <[email protected]>

gradle.properties

@@ -1,5 +1,5 @@
 ltrVersion = 1.5.4
-elasticsearchVersion = 7.12.0
+elasticsearchVersion = 7.12.1
 luceneVersion = 8.8.0
 ow2Version = 8.0.1
 antlrVersion = 4.5.1-1