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-socket.c

@@ -637,14 +637,14 @@ static CURLcode bindlocal(struct Curl_easy *data, struct connectdata *conn,
        * of the connection. The resolve functions should really be changed
        * to take a type parameter instead.
        */
-      uint8_t ip_version = (af == AF_INET) ?
-                           CURL_IPRESOLVE_V4 : CURL_IPRESOLVE_WHATEVER;
+      uint8_t dns_queries = (af == AF_INET) ?
+                            CURL_DNSQ_A : (CURL_DNSQ_A|CURL_DNSQ_AAAA);
 #ifdef USE_IPV6
       if(af == AF_INET6)
-        ip_version = CURL_IPRESOLVE_V6;
+        dns_queries = CURL_DNSQ_AAAA;
 #endif
 
-      (void)Curl_resolv_blocking(data, host, 80, ip_version, transport, &h);
+      (void)Curl_resolv_blocking(data, dns_queries, host, 80, transport, &h);
       if(h) {
         int h_af = h->addr->ai_family;
         /* convert the resolved address, sizeof myhost >= INET_ADDRSTRLEN */