feat(lib/hashring): add logs to hash ring membership wait

[thijmv]

This PR improves observability for the hashring waitForContains method by adding logs to both paths.

[Copilot]

Pull request overview

Improves observability of hash ring membership convergence by emitting structured logs from ring.WaitForContains on both success and timeout paths.

Changes:

• Add structured error log when WaitForContains times out.
• Add structured info log (including elapsed duration) when WaitForContains succeeds.
• Store elapsed duration in a local variable before recording the membership-wait histogram.

Comments suppressed due to low confidence (1)

lib/hashring/ring.go:165

• The timeout log doesn’t include the actual time spent waiting. Since this change is specifically for observability, consider logging the elapsed duration (and optionally recording the histogram) on the error path too, so it’s easy to compare “waited” vs configured timeout when debugging slow/failed membership convergence.

	if err := backoff.Retry(operation, backoff.WithContext(b, ctx)); err != nil {
		log.With("addr", addr, "error", err, "timeout", r.config.MembershipWaitTimeout).Error("Timed out waiting to find address in hash ring")
		return fmt.Errorf("timed out waiting for membership: %w", err)

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