raft: add the concept of quorum supported expiration

[arulajmani]

This patch adds the concept of QSE to {Majority,Joint}Config. For a majority config, the QSE is defined as the leader's maximum supported store liveness expiration across all quorums, where the value for each quorum is the minimum across all replicas, from the perspective of an oracle. For joint configurations, the QSE is the minimum across both its LHS and RHS.

Closes https://github.com/cockroachdb/cockroach/issues/125263

Release note: None