[Test] testLargeClusterStatePublishing - bound max shard no to number of nodes and set replica count to 0

ensureGreen sometimes times out due to too many shards and GC kicking in
Parent/child: If _parent field points to a non existing parent type, then skip the has_parent query/filter

Closes #7362
Closes #7349
Parent/child: Add missing support for the field data loading option to the `_parent` field.

Closes #7394
Closes #7402
Mappings: Added support for empty field arrays

Close #7271
Use physical name to compare files from snapshot metadata

The comparison and read code in the BlobStoreIndexShardRepository
used the physicalName and Name in reverse order. This caused
SnapshotBackwardsCompatibilityTest to fail.

This reverts commit 636af40da1ae22d5b7c8a81435987768e9cc3ac9
Indexed Scripts : Change preference and thread option for GetRequest.

This change forces the GetRequest when a script is being loaded from an index
to use preference("_local") and threaded(false) to prevent the script service from
forking for GetRequests.
[TEST] removed AwaitsFix, added checks to make sure indexed scripts are put correctly
[TEST] only bump replicas if we have enough nodes in the cluster
Index templates: Made template filtering generic and extensible via plugins

Added the ability to register template filters that are being applied when a new index is created. The default filter that checks whether the template pattern matches the index name always runs first, additional filters can also be registered so that templates can be filtered out based on custom logic.

Took the chance to add the handy source(Object... source) method to PutIndexTemplateRequest and corresponding builder

Closes #7459
Closes #7454