Update reverse-nested-aggregation.asciidoc

Fixed reverse nested example

Closes #7463
[Test] RecoveryBackwardsCompatibilityTests.testReusePeerRecovery used `gateway.recover_after_nodes:3` but may start only a 2 node cluster
[Tests] add proper error message when BWC test fail due to node.local=true  system property

System properties are typically set via the command line and therefore override the node settings. If one has `node.local=true` or `node.mode=local` it can result in cryptic error messages during the test run.
Use Flake IDs instead of random UUIDs when auto-generating id field

Flake IDs give better lookup performance in Lucene since they share
predictable prefixes (timestamp).

Closes #7531

Closes #6004

Closes #5941
[Tests] add proper error message when BWC client creation fail due to node.local=true  system property

System properties are typically set via the command line and therefore override the node settings. If one has `node.local=true` or `node.mode=local` it can result in cryptic error messages during the test run.
[Tests] ExternalCluster change error message when use local network mode due to wrong system properties
[TEST] Add simple test to test RT Lucene IW settings
[TEST] Use a large threshold to prevent relocations in RecoveryBackwardsCompatibilityTests
Simplify translog interface

get rid of readSource() entirely, it sucked, Operations should be able
to provide the source themselves.

No more TranslogStream headers, you are now required to pass an
StreamInput or StreamOutput for all operations, which means no extra
state is needed and no need to construct new versions when detecting the
version.
Read and write translog op sizes in TranslogStreams

Previously we handled these integers outside of the translog stream
itself, which was very unclean because other code had to know about
reading the size, or about writing the correct header sometimes.

There is some additional code in LocalIndexShardGateway to handle the
legacy case for older translogs, because we need to read and discard the
size in order to maintain the compatibility for the streaming
operations (they did not read or write the size for 1.3.x and earlier).

Additionally, we need to handle a case where the header is truncated
when recovering from disk