feat: support injected clock in ConditionSet for testability

[jamesmt-aws]

Summary

ConditionSet.Set() uses metav1.Now() for LastTransitionTime, which returns real wall clock time. Controllers that check elapsed time since a condition was set using an injected fake clock get incorrect results because the condition timestamp and the controller clock diverge.

Add a WithClock option to ConditionTypes.For():

// Production (default, no change required)
conditions := status.NewReadyConditions(...).For(object)

// Tests with fake clock
conditions := status.NewReadyConditions(...).For(object, status.WithClock(fakeClock))

Defaults to clock.RealClock{}, so existing callers are unaffected.

Motivation

This fixes a class of test flakes in downstream projects. In kubernetes-sigs/karpenter, the termination controller checks c.clock.Since(condition.LastTransitionTime) using a fake clock, but LastTransitionTime was stamped with metav1.Now(). The test "should not finish draining until minDrainTime has passed" fails deterministically because the fake clock and real clock diverge (kubernetes-sigs/karpenter#2951).

The downstream workaround is to track timestamps separately using the injected clock, duplicating what LastTransitionTime already provides. This PR fixes the root cause.

Changes

• condition_set.go: Add clock field to ConditionSet, ForOptions/ForOption/WithClock types, now() helper. Replace two metav1.Now() calls with c.now().
• condition_set_test.go: Test that WithClock controls LastTransitionTime on set, transition, and same-status update.

Test plan

• All existing tests pass (no behavioral change without WithClock)
• New test verifies fake clock controls LastTransitionTime

[tzneal]

lgtm