[TEST] make sure rest tests info is printed for any @Rest annotated test

We introduced the @Rest annotation a while ago for REST tests (see #7795), we have then to make sure that relevant info to reproduce failures gets printed out for any test that is marked with such annotation, not only for ElasticsearchRestTests

Closes #8680
[Docs] Fix missing comma in mapping
[TEST] remove duplicated tests.slow from randomized testing maven plugin conf
Test: UpdateTests.stressUpdateDeleteConcurrency shouldn't turn off threaded operations

This may result in all network threads being busy for too long.
[HEALTH] Don't mark health as timed out if desired state is reached

Today we mark cluster health requests as timed out if the request has already
timed out. Yet, and implementation detail of the health request is that we are
waiting for events which can take quite some time if the machine is busy. If
we have already reached a valid state while waiting for events to be processed
we shouldn't mark the clusterstate as timed-out. This will help tests that
wait for green state with lots of nodes and shards to not fail the cluster health
calls.
[CLIENT] Only fetch the node info during node sampling

Today we are fetching a lot of information that is unneeded
for the sampling phase. We only really need the DiscoveryNode
to ensure the node is still there.
This commit clears all flags to be false on the NodeInfo call.
Test: predefine sort fields in mapping, otherwise during the test the field may not be found if it were to be introduced dynamically at index time.
[docs] explain default settings for parameters of decay functions

relates to #8624
[Docs] Fix missing new line
[Docs] fix consistency between examples
Add java documentation for aggregations

Buckets:
--------

* terms
* range
* global
* filter
* filters
* missing
* nested
* reverse-nested
* children
* significant-terms
* daterange
* iprange
* range
* histogram
* datehistogram
* geodistance
* geohashgrid

Metrics:
--------

* min
* max
* sum
* avg
* stats
* extendedstats
* valuecount
* percentiles
* percentile-rank
* cardinality
* geobounds