The PROSCRIBED lease status, just like EXPIRED, puts a lease to a definitely
invalid state. The UNUSABLE state (when request timestamp is in stasis period)
is less of a clear cut: we still own the lease but callers may use or not use
it depending on context.

For example, the closed timestamp side-transport ignores the UNUSABLE state
(because we still own the lease), and takes it as usable for its purposes.
Because of the order in which the checks were made, this has lead to a bug: a
PROSCRIBED lease is reported as UNUSABLE during stasis periods, the closed
timestamp side-transport then considers it usable, and updates closed
timestamps when it shouldn't.

This commit fixes the bug by swapping the order of checks in the leaseStatus
method. The order now goes from "hard" checks like EXPIRED and PROSCRIBED, to
"softer" UNUSABLE, and (when the softness is put to the limit) VALID.

Fixes #98698
Fixes #99931
Fixes #100101
Epic: none

Release note (bug fix): a bug is fixed in closed timestamp updates within its
side-transport. Previously, during asymmetric partitions, a node that transfers
a lease away, and misses a liveness heartbeat, could then erroneously update
the closed timestamp during the stasis period of its liveness. This could lead
to closed timestamp invariant violation, and node crashes; in extreme cases
this could lead to inconsistencies in read-only queries.

Epic: none
Release note: none