[TEST] only expand to 1 replica in SnapshotBackwardsCompatibilityTest
Test: Increase the ping timeout to avoid that a candidate master node makes the decision to elect itself too soon.
[Tests] add a debug logging message when starting an external node
[TEST] Fix RandomScoreFunctionTests#testConsistentHitsWithSameSeed
[CORE] Make network interface iteration order consistent

Today the iteration order of the interfaces might change across JVMs
this commit cleans up the NetworkUtils class and attempts to ensure
consistent iteration order across JVMs.
Validate create index requests' number of primary/replica shards

Fixes #7495