[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
[Engine] Verify checksums on merge

Enable lucene verification of checksums on segments before merging them.
This prevents corruption from existing segments from silently slipping into
newer merged segments.

Closes #7360