[RORDEV-1520] Loading ROR settings logic refactoring

[coutoPL]

In this PR:

1. refactoring: ROR config is now ROR settings (we still use the word "config" in the context of ES config)
2. EsConfigBasedRorSettings was introduced. It holds all elasticsearch.yml-related ROR settings and/or ROR properties settings. Anything that ROR needs to know before starting. These settings cannot be reloaded. MainRorSettings and TestRorSettings are reloadable.
3. Loading ROR settings logic was refactored:
   a) ROR defines now the SettingsSource interface. Its implementations define the way ROR reads and saves settings
   b) ROR defines now the StartingRorSettingsLoader interface. It defines how to load the Main & Test ROR settings
   c) The loading retry strategy was decoupled from the loading logic
   d) ROR settings auto-reloader from the RorInstance logic code
4. Unused RRConfig action (and the code related) was removed
5. Some tests improvements related to the new loading settings logic