Merge #3539

3539: Refactor inbound-governor, expand its documentation r=coot a=coot

- inbound-governor: remote hot → warm transition
- inbound-governor: RemotePromotedToHot
- inbound-governor: refactoring
- inbound-governor: use FirstToFinish more prominently
- inbound-governor: EventSignal
- inbound-governor: document the state machine


Co-authored-by: Marcin Szamotulski <[email protected]>

Author: iohk-bors[bot]