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