Add rate limiter for backup request

[levy5307]

Feature Request

Previously, we implemented a feature which name is backup request. And we don't add a rate limiter for it. So it will cause jitter if it's qps or throughput is too large.

In the implementation of backup request, it will only accept the first response it receives. Which means if we reject a backup request immediately after server receives it, the response corresponding to the request which sending to primary replica will be ignored. So we can't simply reject the backup request when it is received.

One way to deal with this problem is adding a rate limiter on client side. But there is a problem that we can't easily change the limiting values according to the actual situation.

In my opinion, we should add rate limiter on server side. And we may don't send a response to the backup request that has been limited. In this way, client will not receive a response corresponding to the backup request, and it can wait for the response from primary replica.