[TEST] wait unitl all machines joined the cluster
Docs: add randomizedtesting-runner to testing-framework.asciidoc

Close #8450
[ALLOCATION] Speed-up disk-threshold decider

Instead of iterating all shards of all indices to get all relocating
shards for a given node we can just use the RoutingNode#shardsWithState
method and fetch all INITIALIZING / RELOCATING shards and check if they
are relocating. This operation is much faster and uses pre-build
data-structures.

Relates to #6372
Fix `cluster.routing.allocation.disk.include_relocations` setting

This setting was incorrectly backported and as a result, was dynamically
settable, but the new setting never actually took effect.
Add TRACE logging to translog operations
docs: add pgp key to repositories page