Sync TLS interception secrets to Envoy via SDS

Now that support for syncing k8s secrets to Envoy via SDS exists, we should use that also for TLS interception secret sync.

References:
- [PR 9486: Envoy TLS support with header imposition](https://github.com/cilium/cilium/pull/9486)
- [PR 18894: Add support for CiliumEnvoyConfig CRD](https://github.com/cilium/cilium/pull/18894)
