DoH: improvements

- decode results when individual requests are done
- makes happy eyeballing start asap
- remove doh_resp structures as no longer needed
- remove CURL_DNS_TYPE_NS, CURL_DNS_TYPE_CNAME and
  CURL_DNS_TYPE_DNAME from DoH
- DoH: do not set PIPEWAIT and SSL OPTS when url starts with http:
- mark Doh master handle as dirty after every sub-request, not only the last
- Doh: start probe on AAAA before A (was the other way).

cf-dns: set EXPIRE_HAPPY_EYEBALLS timer when waiting 50ms on AAAA
result or progress will not be triggered in time.

Add debug env var CURL_DBG_HE_AAAA_AWAIT_MS to override the
default 50ms on waiting for the AAAA result to arrive.

test2100: set CURL_DBG_HE_AAAA_AWAIT_MS to 60 seconds to
provide enough time for slow CI runs to sent all DoH requests.

closes #22514

docs/libcurl/libcurl-env-dbg.md

@@ -174,6 +174,11 @@ a multi handle is destroyed. This implicitly triggers for easy handles
 that are run via easy_perform. The value of the environment variable
 gives the shutdown timeout in milliseconds.
 
+## `CURL_DBG_HE_AAAA_AWAIT_MS`
+
+Overrides the time delaying a connect for AAAA resolve results to arrive
+before continuing with Happy Eyeballing.
+
 ## `CURL_DBG_RESOLV_MAX_THREADS`
 
 Overrides the maximum number of threads for resolver.