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/httpsrr.h

@@ -51,13 +51,15 @@ struct Curl_https_rrinfo {
   size_t ipv6hints_len;
   unsigned char alpns[MAX_HTTPSRR_ALPNS]; /* keytag = 1 */
   /* store parsed alpnid entries in the array, end with ALPN_none */
-  int port; /* -1 means not set */
+  uint16_t port; /* -1 means not set */
   uint16_t priority;
   BIT(no_def_alpn); /* keytag = 2 */
+  BIT(mandatory); /* keytag = 0 */
+  BIT(port_set); /* port value has been assigned */
+  BIT(complete); /* values have been successfully assigned */
 };
 
-CURLcode Curl_httpsrr_set(struct Curl_easy *data,
-                          struct Curl_https_rrinfo *hi,
+CURLcode Curl_httpsrr_set(struct Curl_https_rrinfo *hi,
                           uint16_t rrkey, const uint8_t *val, size_t vlen);
 
 struct Curl_https_rrinfo *
@@ -77,10 +79,17 @@ void Curl_httpsrr_cleanup(struct Curl_https_rrinfo *rrinfo);
 #define HTTPS_RR_CODE_IPV6            0x06
 
 #ifdef USE_ARES
-CURLcode Curl_httpsrr_from_ares(struct Curl_easy *data,
-                                const ares_dns_record_t *dnsrec,
+CURLcode Curl_httpsrr_from_ares(const ares_dns_record_t *dnsrec,
                                 struct Curl_https_rrinfo *hinfo);
 #endif /* USE_ARES */
+
+#ifdef CURLVERBOSE
+void Curl_httpsrr_trace(struct Curl_easy *data,
+                        struct Curl_https_rrinfo *hi);
+#else
+#define Curl_httpsrr_trace(a,b)     Curl_nop_stmt
+#endif
+
 #endif /* USE_HTTPSRR */
 
 #endif /* HEADER_CURL_HTTPSRR_H */