The Ingress namespace/name and UID do not change, so we cannot depend
on those fields alone.

- For each endpoint update, consider an Ingress update.
- For the candidate Ingress, compute the VCL spec.
- Compute a canonical form for VCL specs.
- Compute a hash for a VCL spec.
- The Ingress is updated if the canonical form of its VCL spec is
  not deeply equal to the current VCL spec.
- VCL configs are identified by the hash (in addition to namespace/name
  and UID of the Ingress).