https-rr: implementation improvements

- fold DoH and async HTTPS-RR handling into common code.
  have common cleanups, etc. Have a CURLcode result in async
  handling to allow HTTPS RR parsing to fail.
- keep target, ipv4hints, ipv6hints, port and echconfig also
  when resolving via cares. We need to know `target` and `port`
  when evaluating possible ALPN candidates to not go astray.
- add CURL_TRC_DNS for tracing DNS operations
- replace DoH specific tracing with DNS, use doh as alias
  for dns in curl_global_tracea()

Closes #16132

scripts/singleuse.pl

@@ -47,6 +47,7 @@ my %wl = (
     'Curl_creader_def_close' => 'internal api',
     'Curl_creader_def_read' => 'internal api',
     'Curl_creader_def_total_length' => 'internal api',
+    'Curl_trc_dns' => 'internal api',
 );
 
 my %api = (