Spec: Fixes URL links to documentation

Closes #8656
Docs: Adds documentation for indices.exists_template

Closes: #8657
Update to Jackson 2.4.3

- Update pom to 2.4.3 from 2.4.2
- Enable the CBOR data header (aka tag) from the CBOR Generator to provide binary identification like the Smile format
- Check for the CBOR header and ensure that the data sent in represents a "major type" that is an object
- Cleans up `JsonVsCborTests` unused imports
Fix for geohash neighbors when geohash length is even.
We don't have to set XLimit and YLimit depending on the level (even or odd), since semantics of x and y are already swapped on each level.
XLimit is always 7 and YLimit is always 3.

Close #8526
Adding unit test for even / odd boundary condition
Revert "Update to Jackson 2.4.3"

This reverts commit 7523d0b150ff7b05aa37b5e6edf8216341671b38.
Core: clarify index removal log message
Raise REST test Timeout - LocalGW takes it't tall...
Core: Let the disk threshold decider take into account shards moving away from a node in order to determine if a shard can remain.

By taking this into account we can prevent that we move too many shards away than is necessary.

Closes #8538
Closes #8659
Core: separately log file deletions

Today, you can turn on lucene.iw TRACE logging, but that produces tons
of output.  This changes breaks out separate lucene.iw.ifd and
index.store.deletes logger components (TRACE), disabled by default, to
see what part of Elasticsearch is deleting index files.

Closed #8662

Closed #8603
[TEST] Add additional logging to memoryCircuitBreaker test
Updated docs to use v1.4.1 as current
Versions: Add 1.4.2/1.3.7 constants
[TEST] Stabelize FunctionScoreBWC tests - allocation should be disabled during upgrade
[TEST] Wait for green before testing IW settings
[TEST] split base settings in ClusterDiscoveryConfiguration between node and transport client

The default settings that are currently applied to the transport client are about discovery and gateway, modules that are not even loaded on the transport client. We can now remove the local gateway as it's not the default one anyway. Also, make sure that the discovery setting is only applied to the node, as it is not relevant for transport client.

Closes #8653
[TEST] Extend unicast ports generation to support more concurrent clusters

Make it possible to run multiple tests with unicast configuration, by assigning ports based on their test scope.
Every jvm still gets its own port range based on the jvm id, but we now make sure that the different jvms ranges never overlap. The global cluster gets a reserved port range, while SUITE and TEST scopes are treated equally, just assuming that they never run concurrently on the same jvm, thus ports can be safely reused.

Closes #8634
[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