Support consistent read with leader lease

[drmingdrmer]

Openraft has a mechanism called leader lease. This mechanism ensures that a follower does not elect itself as a leader before a certain period of time, which is determined by adding the timer_config.leader_lease + timer_config.election_timeout. The follower refreshes the lease by updating the last-updated-time of the vote. However, the current issue is that the leader does not update the lease yet.

To support reading consistent state, openraft needs to :

• The leader should extend its lease when a log is accepted by a quorum.
• and add a public API such as Raft::read(sm: &mut impl RaftStateMachine) that atomically checks leader lease and reads some data from the state machine.

https://github.com/datafuselabs/openraft/blob/54154202beec3e2de433044baae505cc80db375b/openraft/src/core/raft_core.rs#L1345-L1357

https://github.com/datafuselabs/openraft/blob/54154202beec3e2de433044baae505cc80db375b/openraft/src/engine/handler/vote_handler/mod.rs#L124

Originally posted by @drmingdrmer in #262 (comment)

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