Address all the remaining review comments

- Improve the names for categories and states
- Remove restarted/reconfigured states
- Add a configuration for delay between restarts
- Add a configuration for delay between restart and trigger of preferred leader election
- Restart NOT_RUNNING nodes in parallel for quicker recovery
- Improve the overall algorithm section, to make it clearer and concise

Signed-off-by: Gantigmaa Selenge <tina.selenge@gmail.com>