This change adapts x-pack to pass on the parsed XContentType from rest requests to transport
requests and use this value in place of attempting to auto-detect the content type.
Original commit: elastic/x-pack-elasticsearch@57475fd403
Fixes to x-plugins code now that DateMathParser accepts a LongSupplier rather than a Callable to get the value of now
Relates to elastic/elasticsearchelastic/elasticsearch#20796
Original commit: elastic/x-pack-elasticsearch@99fc47a8a7