double confirm or print warn information when set max-replica to less than 3

[AndreMouche]

Enhancement Task

when we set the max-replica less than 3( mostly may be a mistake and carries high risk) with pd-ctl:

 tiup ctl:v7.5.2 pd config set max-replicas 2
Starting component ctl: /home/tidb/.tiup/components/ctl/v7.5.2/ctl pd config set max-replicas 2
Success!

As you may know, Setting max-replica to less than 3 may be a mistake and carries high risk, and I think we would better print some warning information( or let the customer do a second confirm) to alert the customer that this behavior carries high risk.