[TEST] Reimplement AckTests#testDeleteWarmerNoAcknowledgement

This test was not testing what it was supposed to test. This commit
implements the test as an actual delete warmer test without ack
returned.
[TEST] close REST test execution context only if not null

The context can be null when REST tests are disabled via sysprop.
[DOC] Add GET Alias API note to breaking changes

Note explains that GET Alias API now supports IndicesOptions and will error if a index is missing
[TEST] allow to fully disable REST tests included parsing via -Dtests.rest=false

We currently look for REST tests on file system although they are disabled. We should not do that and move the check earlier on. This way third parties using our test infra, which don't have REST tests on file system, can effectively disable the REST tests, otherwise they would get initialization error despite having disabled them.  The downside is that the number of tests visualized is going to be zero instead of the real number of parsed REST tests, but there is nothing we can do about this. Tests get ignored anyways.
[ENGINE] try increment store before searcher is acquired

InternalEngine#refreshNeeded must increment the ref count on the
store used before it's checking if the searcher is current since
internally a searcher ref is acquired and if that happens concurrently
to a engine close it might violate the assumption that all files
are closed when the store is closed.

This commit also converts some try / finally into try / with.
[TEST] move REST tests to their own test group

Closes #7795
Bulk API: Do not fail whole request on closed index

The bulk API request was marked as completely failed,
in case a request with a closed index was referred in
any of the requests inside of a bulk one.

Implementation Note: Currently the implementation is a bit more verbose in order to prevent an instanceof check and another cast - if that is fast enough, we could execute that logic only once at the beginning of the loop (thinking this might be a bit overoptimization here).

Closes #6410
Bulk Request : Add Document Request

This file was missing.
Revert "Bulk API: Do not fail whole request on closed index"

This reverts commit 405e5816b827db5823e6c2ed9c1bbe9fa4629355.
Revert "Bulk Request : Add Document Request"

This reverts commit 86f575dcea31e2e1486a17ed248708084905aeea.
Bulk API: Do not fail whole request on closed index

The bulk API request was marked as completely failed,
in case a request with a closed index was referred in
any of the requests inside of a bulk one.

Implementation Note: Currently the implementation is a bit more verbose in order to prevent an instanceof check and another cast - if that is fast enough, we could execute that logic only once at the
beginning of the loop (thinking this might be a bit overoptimization here).

Closes #6410
Internal: remove ForceSyncDirectory

Historical code, not used anymore.

Closes #7804
Core: Check if from + size don't cause overflow and fail with a better error.

Closes #7778
Discovery: Give a unique id to each ping response

During discovery a node gossips with other nodes to discover the current state of the cluster - what nodes are out there, what version they use and most importantly whether there is an active master out there. During this ping process we may end up in a situation where old information is mixed with new. This is comment if a couple of master election happen in rapid succession.

This commit adds a monotonically increasing id to each ping response. This makes it easy to always select the last ping from every node.

Closes #7769
Test: RecoveryWhileUnderLoadTests.recoverWhileRelocating should report cluster state when failing to reach green
Recovery: mapping check during phase2 should be done in cluster state update task

Before phase2 we check verify that the local mapping is in sync with the cluster state mapping (and send & wait on a master update mapping task if not). This check should be done under a cluster state update task to make sure an incoming cluster state update to do not change things while we check.

Closes #7744
Tests: extend testRecoverFromPreviousVersion to sometimes index during relocation

Relates to #7729

Closes #7768
Apply bulk change to 1.3.3

relates to #7729
[TEST] Ensure primaries are allocated before bulk indexing with dymamic mappings
[RECOVERY] Mark last file chunk to fail fast if payload is truncated

Today we rely on the metadata length of the file we are recoverying
to indicate when the last chunk was received. Yet, this might hide bugs
on the compression layer if payloads are truncated. We should indicate
if the last chunk is send to make sure we validate checksums
accordingly if possible.

Closes #7830