[TESTS] Additional logging for `testThreadedUpdatesToChildBreakerWithParentLimit`
[TEST] create client nodes using node.client: true instead node.data: false and node.master: false

Create client nodes using `node.client: true` instead of `node.data: false` and `node.master: false`.

We should create client nodes in our test infra using the `node.client:true` settings as that is the one that users use, and the one that we use as well in `ClientNodePredicate` thus we end up not finding client nodes otherwise as they weren't created with the proper setting.

Updated also the `DataNodePredicate` so that `client: true` is enough, no need for `data: false` as well.

Closes #7911
[TEST] make sure that IndicesRequestTests is repeateable using the same seed

Remove the creation of a node client if not there before each test through setup method. `numClientNodes` makes sure that the client node gets created during suite cluster initialization.
MLT Query: Support for artificial documents

Previously, the only way to specify a document not present in the index was to
use `like_text`. This would usually lead to complex queries made of multiple
MLT queries per document field. This commit adds the ability to the MLT query
to directly specify documents not present in the index (artificial documents).
The syntax is similar to the Percolator API or to the Multi Term Vector API.

Closes #7725
[TEST] Use Shutdown API only if nodes are on 1.3.3 or newer to prevent shutdown problems
1.3.3 release: add 1.3.4 version constant
[BUILD] Release version should match latest version

This commit ensures that the latest version in our code is identical
to the project.version specified in the pom.xml file.
Nest original exception while creating NoShardAvailableActionException

Closes #7756
Fix optimize behavior with 'force' and 'flush' flags.

This does the following:
* Make 'force' flag only build a merge if the delegate MP returned no merges
* Add async handling for 'flush' when 'waitForMerges' is false
* Remove flush at the beginning of optimize.  This is something the user can
  do if they wish, before calling optimize.

closes #7886
closes #7904
closes #7920
Move forbidden api signature files to dev-tools.

This avoids the files showing up in the binary release, since .txt files
are copied.

closes #7917
closes #7921
[TEST] Mute MoreLikeThisActionTests#*ArtificialDocs
Core: go back to unbounded (scaling) thread pool for management threads (revert #7318)
Indices API: fixes GET Alias API backwards compatibility

For just the case when only the aliases are requested, the default indices options are to ignore missing indexes. When requesting any other feature or any combination of features, the default will be to error on missing indices.

Closes #7793