[snrc resolver] owned by endpoint and expiry

[brenzi]

closes #1821

New features:

• new owned-by endpoint, returning all names owned by a given ETH address. This is needed to scan a recovered key for the names it owns
• handle expiry:
  • report expires for resolved names, also the grace period
  • do not resolve expired names, but give meaningful error status
• query by labelhash instead of plaintext name to prevent front-running when trying names using the resolver
• return reserved status with a reason why the name has been reserved (currently a hardcoded reason, to be extended in the future)

Maturity:

• some security hardening (fixing adversarial review findings)
• add to this repo's CI

This PR is non-breaking (with the intended exception that expired names no longer get resolved as success, but as error with details)