Catch both FileNotFound & NoSuchFileException
MLT Query: versatile 'like' parameter

The MLT query has a lot of parameters. For example, a set of documents is
specified with either `like_text`, `ids` or `docs`, with at least one
parameter required. This commit groups all the document specification
parameters under one called `like`. The syntax is described below and could
easily be extended to allow for new means of specifying document input. The
`like_text`, `ids` and `docs` parameters are deprecated.

As a single piece text:

{
  "query": {
    "more_like_this": {
      "like": "some text here"
    }
  }
}

As a single item:

{
  "query": {
    "more_like_this": {
      "like": {
        "_index": "imdb",
        "_type": "movies",
        "_id": "88247"
      }
    }
  }
}

Or as a mixture of all:

{
  "query": {
    "more_like_this": {
      "like": [
        "Some random text ...",
        {
          "_index": "imdb",
          "_type": "movies",
          "_id": "88247"
        },
        {
          "_index": "imdb",
          "_type": "movies",
          "doc": {
            "title": "Document with an artificial title!"
          }
        }
      ]
    }
  }
}

Closes #8039
Test: testRecoverFromPreviousVersion should refresh from new nodes if running against v<1.3.0

This is due to a bug in older version causing refreshes to potentially be missed due to relocations #6545

Also:
- Changed test to keep track of ids and report missing ones.
- Removed total count check from assertSearchHits in order to enable per id checks in cased of a mismatch
- Added a printable unique id part the ids of dummy documents added by indexRandom. The current random unicode id
sometimes prints as ???? to the logs making them hard to trace
[TEST] `Scope.SUITE` is not reproducible due to late cluster initialization

The cluster for `Scope.SUITE` tests must be initialize in a static manner
before the first test runs otherwise the random context used to initialize
the cluster is taken from tests randomness rather than the suites randomness.
This means test clusters will have different setups if only a single test is
executed or even the test might have a entirely different random sequence.
add missing imports
[TEST] NettyTransportMultiPortIntegrationTests used wrong random to
initialize ports.

JUnit uses an instance per test which caused the prot range to be
initialized twice since suite level tests are not configured in a
different context.
Recovery: RecoveriesCollection.findRecoveryByShard should call recoveryStatus.tryIncRef before accessing fields

The function iterates over a snapshot of on going recoveries and thus may access RecoveryStatus objects that are already finished.

Closes #8231
Core: Validates bool values in yaml for node settings

- Added parseBooleanExact in booleans which throws exception in case of
  parse failure
- Used ParseExact in static's to make it consistent

+ code review fixes

- Added unit test
- Changed Exception Type to ElasticSearchIllegalArg from Parse
- used isExplicit*

Closes #8097
[TEST] Add test for #8226
Cat API: Add node name to _cat/recovery

Add source_node and target_node fields to the recovery cat API. Also fixed and updated the documentation which was not complete concerning fields names.

Closes #8041
[TESTS Fix wrong assertion in test introduced by #8128
Aggregations: Return the sum of the doc counts of other buckets.

This commit adds a new field to the response of the terms aggregation called
`sum_other_doc_count` which is equal to the sum of the doc counts of the buckets
that did not make it to the list of top buckets. It is typically useful to have
a sector called eg. `other` when using terms aggregations to build pie charts.

Example query and response:

```json
GET test/_search?search_type=count
{
  "aggs": {
    "colors": {
      "terms": {
        "field": "color",
        "size": 3
      }
    }
  }
}
```

```json
{
   [...],
   "aggregations": {
      "colors": {
         "doc_count_error_upper_bound": 0,
         "sum_other_doc_count": 4,
         "buckets": [
            {
               "key": "blue",
               "doc_count": 65
            },
            {
               "key": "red",
               "doc_count": 14
            },
            {
               "key": "brown",
               "doc_count": 3
            }
         ]
      }
   }
}
```

Close #8213
[TEST] Beef up test and replace deprecated API
Test: remove wait on events from multipleNodesShutdownNonMasterNodes

The test validates that minimum master node is honored after shutting down nodes. When nodes are restarted we may go through a couple of master election of a master is elected and  discovers some of the old nodes left before all new node have joined. Processing that node failure the master de-elects it self, which is fine because we will start a new master election. Test however runs a clusterHealth call with a  wait for event. This is implemented using a cluster state update task which fails when the master steps down. Longer term fix requires a rewrite of the cluster health API code but a quick fix is not check for events (not needed for this test).
Core: Cleanup non nested filter to not flip the bits in the FixedBitSet returned by the wrapped filter.

If the filter producing the FBS were to be cached then it would flip bits each time the NonNestedDocsFilter was executed.
In our case we cache the NonNestedDocsFilter itself so that didn't happen each time this filter was used.
However the hashcode of NonNestedDocsFilter and NestedDocsFilter was the same, since NonNestedDocsFilter directly used NestedDocsFilter#hashCode()

Closes #8227
Closes #8232
[CORE] remove usage of Directory#fileExists

This commit removes the usage of #fileExists which has been
deprecated long ago an can be a source of race conditions.
Remove unused imports