lib: make resolving HTTPS DNS records reliable:

- allow to specify when they are wanted on starting a resolve
- match dns cache entries accordingly. An entry which never
  tried to get HTTPS-RRs is no answer for a resolve that wants
  it.
- fix late arrivals of resolve answers to match the "async"
  records that started them - if it still exists.
- provide for multiple "async" resolves in a transfer at the
  same time. We may need to resolve an IP interface while the
  main connection resolve has not finished yet.
- allow lookup of HTTPS-RR information as soon as it is
  available, even if A/AAAA queries are still ongoing.

For this, the "async" infrastructure is changed:

- Defined bits for DNS queries `CURL_DNSQ_A`, `CURL_DNSQ_AAAA`
  and `CURL_DNSQ_HTTPS`. These replace `ip_version` which says
  nothing about HTTPS.
  Use them in dns cache entries for matching.
- enhance the `async->id` to be a unique `uint32_t` for
  resolves inside one multi. This is weak, as the id may
  wrap around. However it is combined with the `mid` of
  the easy handle, making collisions highly unlikely.
  `data->state.async` is only accessed in few places where
  the mid/async-id match is performed.
- vtls: for ECH supporting TLS backends (openssl, rustls, wolfssl),
  retrieve the HTTPS-RR information from the dns connection filter.
  Delay the connect if the HTTPS-RR is needed, but has not
  been resolved yet.

The implementation of all this is complete for the threaded
resolver. c-ares resolver and DoH do not take advantage of
all new async features yet. To be done in separate PRs.

Details:

c-ares: cleanup settings and initialisation. Any ares channel
is only being created on starting a resolve and propagating
operations in setopt.c to the channel are not helpful.

Changed threaded+ares pollset handling so that they do not
overwrite each others `ASYNC_NAME` timeouts.

Add trace name 'threads' for tracing thread queue and
pool used by threaded resolver.

Closes #21175

lib/cf-https-connect.c

@@ -330,13 +330,6 @@ static CURLcode cf_hc_resolv(struct Curl_cfilter *cf,
      * can no longer change that. Any HTTPSRR advice for other hosts and ports
      * we need to ignore. */
     const struct Curl_https_rrinfo *rr;
-    bool need_https_rr = FALSE;
-
-    if(need_https_rr) {
-      result = Curl_conn_dns_result(cf->conn, cf->sockindex);
-      if(result)
-        return result;
-    }
 
     /* Do we have HTTPS-RR information? */
     rr = Curl_conn_dns_get_https(data, cf->sockindex);
@@ -346,7 +339,7 @@ static CURLcode cf_hc_resolv(struct Curl_cfilter *cf,
         !rr->target[0] ||
         (rr->target[0] == '.' &&
          !rr->target[1])) &&
-       (rr->port < 0 ||    /* for same port */
+       (!rr->port_set ||    /* for same port */
         rr->port == cf->conn->remote_port)) {
       for(i = 0; i < CURL_ARRAYSIZE(rr->alpns) &&
                  alpn_count < CURL_ARRAYSIZE(alpn_ids); ++i) {