Update scripting.asciidoc

Added an ID for native java scripts
[TEST] Reduce the number of threads in StressUpdateDelete test.
Fix InternalSearchHits serialization to be deterministic

The assertion on binary equality for streamable serialization
sometimes fails due to the usage of identify hashmaps inside
the InternalSearchHits serialization. This only happens if
the number of shards the result set is composed of is very high.
This commit makes the serialziation deterministic and removes
the need to serialize the ordinal due to in-order serialization.