Add DomainVerificationProxyV1

Backporting the new per-domain state to the old v1 intent filter
verification agent API.

Uses a new STATE_LEGACY_FAILURE to track the failedDomains returned by
the v1 verification agent, to support per-domain state with the old API.

Exempt-From-Owner-Approval: Already approved by owners on main branch

Bug: 170321181

Test: TBD in later change when proxies are combined

Change-Id: I2953f7e0100d425dcb806c607fdeae101803d8f4