Implement Address Validation Token and send when 0-RTT is enabled

## The problem
The point of anti-amplification is to limit the amount of data sent before validating the address. An address is validated during connection establishment by receiving a Handshake packet.

However, when processing a request in 0-RTT, we could potentially want to send more than anti-amplification limit worth of data. Anti-amplification blocking a 0-RTT request reduces the effectiveness of the feature.

## Proposed fix
> A server MAY provide clients with an address validation token during one connection that can be used on a subsequent connection. Address validation is especially important with 0-RTT because a server potentially sends a significant amount of data to a client in response to 0-RTT data.

As the RFC calls out, we might want to implement [Address validation tokens](https://www.rfc-editor.org/rfc/rfc9000.html#section-8.1.3) and issue then when issuing 0-RTT enabled resumption tickets.

Start with RFC 9000 section 8.1.3, then locate quiche's 0-RTT resumption-ticket issuance and connection-establishment paths. Trace where address validation is handled and define the token flow for a subsequent connection; done should include issuing tokens with 0-RTT-enabled tickets and using them to avoid unnecessary anti-amplification blocking.

Written by the indexing model from the issue text.