ClickHouse: detect config changes that require restart

[GrigoryPervakov]

Consists of two phases:

1. Ensure the updated config is mounted in the replica
   It can be solved by adding a config revision as a reserved named collection field, so a simple query can be used to get the applied configuration.
2. Detect if the server needs a restart
   For server settings, system.server_settings can be used. For the settings like Kafka/merge tree/etc we always need a restart, so we need another way.
   As an idea, utilize system.warnings and fire the warning that the server needs a restart during the config reloader routine.
   The other way is to implement such logic in the operator, but in this case, it would make it harder to support.