[TRANSLOG] Cut over to Path API

This commit moves all the Translog related code over to the
NIO2 Path API. It also make transaction logs write once since it
never reuses a translog file.

Closes #8611
Typo: changed "5% or the real words" to "5% of the real words"

Closes #8582
Docs: Added swift openstack repository

Closes #8583
[RECOVERY] Throw IndexShardClosedException if shard is closed

Today we throw a generic ElasticsearchException when a recovery is cancled. This
causes verbose logging and send shard failures and additional unnecessary cluster state
events. We can just throw IndexShardClosedException which prevents the send shard failures
Parent/child: Fixed parent/child not being able to be used in alias filters.

Closes #8628
remove unnecessary clearScroll call - these contexts are released by delete index now
[GATEWAY] Cut over MetaDataStateFormat to Path API

Closes #8609
[SPEC] Removed the utilities for generating REST specs/code

The utilities have been migrated to the elasticsearch/elasticsearch-ruby repository.

See: https://github.com/elasticsearch/elasticsearch-ruby/tree/master/elasticsearch-api/utils

Related: elasticsearch/elasticsearch-ruby@dfac51d

Closes #8606
Aggregations: fix rounding issues on DST switch.

Closes #8339.
Scripts: Return new lists on calls to getValues.

Scripts currently share the same list across invocations to getValues. This
caused a bug in script fields where all documents coming from the same segment
would get the same values (basically, for the next document for which script
values have been requested). Scripts now return a fresh new list on every
invocation to `getValues`.

Close #8576
Added note that ES packages automatically change vm.max_map_count

Closes #8601