In 5.x we allowed this with a deprecation warning. This removes the code
added for that deprecation, requiring the cluster name to not be in the
data path.
Resolves#20391
This was an error-prone version type that allowed overriding previous
version semantics. It could cause primaries and replicas to be out of
sync however, so it has been removed.
Resolves#19769
Previous versions of Elasticsearch permitted unquoted JSON field names even though this is against the JSON spec. This leniency was disabled by default in the 5.x series of Elasticsearch but a backwards compatibility layer was added via a system property with the intention of removing this layer in 6.0.0. This commit removes this backwards compatibility layer.
Relates #20388
Igor Motov
Lee Hinman
David Pilato
Jason Tedor
Clinton Gormley