Index Stats: Add support for segments stats
closes #4101
Improve stability of RobinEngineIntegrationTest by reducing direct memory usage of the test env
External method to set rootTypeParsers in DocumentMapperParser incorrect
fixes #4113
Set MaxDirectMemorySize for tests to have consistent upper bounds
Reduce number of documents in RobinEngineIntegrationTest to prevent memory peaks triggering OOM
Guarantee sorted order for [Double|Long|Bytes]Values

Values returned by [Double|Long|Bytes]Values are sorted today which
is guaranteed by the underlying Lucene index. Several implementations can
make use of this property but the interfaces don't guarantee this behavior.
This commit adds the guarantees and makes use of them in several places.

Note: This change might require sorting for 3rd party implemenations of these
interaces.
Move IndexFieldDataServiceTests into corresponding package
Move MockDirectories into o.e.test.store
Move o.e.junit to o.e.test.junit
Move stresstests out of o.e.test
Fixed fetch subphase to not recreate the HitContext for each hit, so that the object cache stays the same

Fixed also bug in the fast vector highlighter which was raised by enabling the object cache, due to null FieldQuery (NPE) in case the objects are taken from the cache

Added tests to check if there are issues when highlighting multiple fields at the same time

Closes #4106
Trimmed down HighlighterSearchTests

Used common assertHighlight and concise mapping whenever possible
More indexRandom too
Fix missing affectation in SimpleChildQuerySearchTests.testParentChildQueriesCanHandleNoRelevantTypesInIndex()
[DOCS] Changed all store:yes/no to store:true/false
which is how this setting is stored internally
[DOCS] Fixed the fielddata regex example on core mapping
Used the actual index_name when making highlighting using the postings highlighter

Previously the field name specified in the search request was used, which isn't correct in case a custom index_name has been used for a field or the "path":"just_name" has been used in the mapping.

 Closes #4116
Reduce number of docs in test for #4093 - 30 docs are enough to trigger the bug
Add wabisabi to Scala clients.
_default_ mapping not applied when using separate master/data nodes
fixes #4124
Unable to create a nested filtered alias on a dataless master
fixes #4112