Add `RDS_CMSG_RXPATH_LATENCY` to `socket`

Feature or enhancement

Proposal:

This issue suggests adding new RDS constants.

s = /* a RDS type socket */
msg, ancdata, flags, addr = s.recvmsg(2048, socket.CMSG_LEN(5 * 128))
for cmsg_level, cmsg_type, cmsg_data in ancdata:
    if cmsg_type == RDS_CMSG_RXPATH_LATENCY:
        # some processing

It‘s used to query the rx-path(that's receive) latency of RDS. Usually used to optimize RDS communication, such as controlling the number of connections and other strategies

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

Linked PRs

• gh-127384

Comece revisando o tratamento de dados auxiliares RDS pelo módulo de socket e o caminho recvmsg descrito na proposta. Verifique o PR vinculado gh-127384 para consultar a implementação atual e qualquer cobertura de testes esperada; considera-se concluído quando a constante RDS_CMSG_RXPATH_LATENCY estiver exposta e puder ser usada com o fluxo de dados auxiliares mostrado.