Fix LeaderElector waiting a full extra lease duration before acquiring an already-expired lease on startup

[Copilot]

On first observing an existing lock record, LeaderElector stamped its internal observedTimeMilliSeconds with the current wall-clock time rather than the record's actual renewTime. This made a freshly-started candidate treat an already-expired lease as still valid for one more full leaseDuration, delaying takeover instead of acquiring it immediately.

• LeaderElector.tryAcquireOrRenew: when the observed record is being set for the very first time (no prior observedRecord), initialize observedTimeMilliSeconds from the record's own renewTime instead of System.currentTimeMillis(). Subsequent observations during normal operation still use the current time, preserving the existing clock-skew tolerance.
• Test: added acquiresAlreadyExpiredLeaseImmediately in LeaderElectorTest, which seeds a lock with a record whose renewTime is well past leaseDuration and asserts a new candidate acquires leadership promptly rather than waiting out an extra lease period.

if (!oldLeaderElectionRecord.equals(this.observedRecord)) {
  boolean firstObservation = this.observedRecord == null;
  this.observedRecord = oldLeaderElectionRecord;
  this.observedTimeMilliSeconds =
      firstObservation
          ? oldLeaderElectionRecord.getRenewTime().getTime()
          : System.currentTimeMillis();
}

• Fixes LeaderElector fails to acquire expired lease on initial run due to missing expiration check #4913

[linux-foundation-easycla]

• ✅ login: brendandburns / name: Brendan Burns (6a86c93)
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[kubernetes-prow]

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