feat(policy): add shard reconnection policies

Add abstract classes: `ShardReconnectionPolicy` and `ShardReconnectionScheduler`
And implementations:
`NoDelayShardReconnectionPolicy` - policy that represents old behavior
of having no delay and no concurrency restriction.
`NoConcurrentShardReconnectionPolicy` - policy that limits concurrent
reconnections to 1 per scope and introduces delay between reconnections
within the scope.

Author: dkropachev