This commit introduces JSON streaming support which
consists of serializing HTTP request with
application/stream+json media type as line delimited JSON.
It also optimize Flux serialization for application/json by
using flux.collectList() and a single Jackson invocation
instead of one call per element previous strategy.
This change result in a x4 throughput improvement
for collection with a lot of small elements.
Issues: SPR-15095, SPR-15104
6b9b0230c4