Feature/7.x/remove upgrade assistant

[Mpdreamz]

This was a one off release.

We need to decide if we want this removed with 7.2 or 7.3 though.

[Mpdreamz]

Test failures:

7.0.0

build.bat seed:9368 integrate 7.0.0 "writable" "rolloverindex,putpipeline"

Rolloverindex test fails due to a mapping problem with the random data on this seed that needs looking into.

PutPipeline failed due to cluster ProcessClusterEventTimeoutException which I've seen happen a couple of times before with this test.

7.0.0-SNAPSHOT

Failed   Tests.Indices.IndexManagement.SplitIndex.SplitIndexApiTests.ReturnsExpectedResponse
Error Message:
 Tests.Framework.EndpointTests.ResponseAssertionException : Expected response.ShardsAcknowledged to be true, but found False.
Response Under Test:
Valid NEST response built from a successful (200) low level call on PUT: /nest-fluentasync-77a092ae/_split/nest-fluentasync-77a092ae-target?pretty=true&error_trace=true
# Audit trail of this API call:
 - [1] HealthyResponse: Node: http://localhost:9200/ Took: 00:00:30.5230768
# Request:
{"settings":{"index.number_of_shards":8}}
# Response:
{
  "acknowledged" : true,
  "shards_acknowledged" : false,
  "index" : "nest-fluentasync-77a092ae-target"
}

shards_acknowledged: false is not common here, need to understand when acknowledged and shards_acknowledged differ and what this means.

Will create new tickets for these.

[Mpdreamz]

Merging this in on my own accord @codebrain @russcam

[Mpdreamz]

This is now also cherry picked to master