Indexed Scripts/Templates : Fix .script index template.

This commit makes the default number of shards for the .scripts index to ````1````, it also
forces the auto_expand replicas to ````1-all````. This change means that script index GET requests to load
scripts from the index should always use the local copy of the scripts index, preventing any network traffic or calls
on script GET.
Indexed Scripts/Templates : Change the default auto_expand to 0-all

This commit changes the auto_expand_replicas setting for the ````.scripts```` index to
0-all from 1-all.
Aggregations: Encapsulate AggregationBuilder name and make getter public

Close #7425
Scan: Use ConcurrentHashMap instead of HashMap, because the readerStates is accessed by multiple threads during the entire scroll session.

Closes #7499
Closes #7478
Core: Remove the warmer listener when the FixedBitSetFilterCache gets closed.
[TEST] Port can have more or less than 4 digits
[TEST] Exclude per commit files rather than only segments_N

When we corrupt a file in the snapshot/restore case we have to corrupt
a per-segment file. The .del file might change with the commit / flush
that is triggered by the snapshot operation.
Client: Make the query builder nullable in filteredQuery.

Close #7398
[TEST] add AwaitsFix for testTranslogChecksums since it may cause OOME
if the size is corrupted
[TEST] Fix per-segment / per-commit exclude logic in CorruptFileTest
Docs: Replace added[1.4.0] with coming[1.4.0] since 1.4 is not released yet.
Docs: Add a migration guide to aggregations.
Suggest API - bugs with encoding multiple levels of geo precision.
1) One issue reported by a user is due to the truncation of the geohash string. Added Junit test for this scenario
2) Another suspect piece of code was the “toAutomaton” method that only merged the first of possibly many precisions into the result.

Closes #7368
[CORE] Don't update indexShard if it has been removed before

Today we have logic that removes a shard from the indexservice if
the shard has changed ie. from replica to primary or if it's recovery
source vanished etc. This can cause shards from been not allocated at
all on a nodes causeing delete requests to timeout since we were waiting
for shards on nodes that got dropped due to a IndexShardMissingException

Closes #7509
Completion suggestion javadocs
[DOCS] Added JavaDocs for ClusterAdminClient, IndicesAdminClient and Warmer API
Highlighter Javadocs
Docs: Add javadocs to the client-side aggregation APIs.
[TEST] fix off-by-one error in BigArrays tests

Comparisons for the BigArrays breaker use "greater than" instead of
"greater than or equal", which was never an issue before because the
test size was not right on a page boundary. A test with an exactly
divisible page boundary (4mb exactly in this case) caused the sizes to
be equal to, but not exceed, the limit, and never break.

The limit should be smaller than the test increments the breaker anyway.
[TEST] Stabelize SimpleRecoveryLocalGatewayTests#testReusePeerRecovery