fix(policy): set observedGeneration in status conditions

[agrawalx]

Set observedGeneration in status conditions

Fixes #14964
Supersedes #14973

Problem

The policy status controller writes status conditions with observedGeneration unset. The Gateway API specification requires implementations to set this field to the resource's metadata.generation when generating status:

Consumers use the field to detect stale status. In particular, Flagger v1.42+ checks condition.observedGeneration < metadata.generation after each route edit to confirm Linkerd has reconciled it. Since Linkerd never sets the field,
the check never passes and canary rollouts stall indefinitely:

HTTPRoute echo-blue.tools parent echo-blue is not ready
(status: True, observed generation: 0, current generation: 1)

Solution

• Track metadata.generation on RouteRef, HttpLocalRateLimitPolicyRef, and EgressNetworkRef; populate it in every apply(). Storing it on the refs (rather than passing it down from apply only) keeps the periodic reconcile path consistent with the watch path.
• Thread the generation through all condition-producing functions (accepted, no_matching_parent, resolved_refs, etc.) so every condition the controller writes carries observedGeneration.
• Add the missing observedGeneration property (standard metav1.Condition shape, mirroring the existing httproute.policy.linkerd.io schema) to the EgressNetwork and HTTPLocalRateLimitPolicy CRD condition schemas.

Validation

• New unit tests (policy-controller/k8s/status/src/tests/):
  • conditions carry the resource's generation for routes, rate-limit policies, and egress networks;
  • a generation bump with an unchanged spec produces a fresh patch carrying the new generation (the signal Flagger consumes), while a re-apply whose status already matches produces no patch (no self-trigger loop).