ext/curl: Add HTTP/3 constants

This intends to supersede the two following PRs:
 - #12000 because it does not modify the stub file, but only update the
   arginfo file. It also proposes to merge to GA branches, and is
   currently marked as Requires RM Approval.
 - #12543 Essentially the same as this PR and from the same author, as
   this, but its about a year old and requires rebasing anyway.

This adds the `CURL_HTTP_VERSION_3` and `CURL_HTTP_VERSION_3ONLY`
constants on relevant versions (7.66 and 7.88 respectively).

It is possible to use HTTP/3 without having these constants declared,
but having them declared in PHP makes things more approachable and
"official".

Author: Ayesh

ext/curl/curl.stub.php

@@ -3102,6 +3102,11 @@
  * @cvalue CURLINFO_RETRY_AFTER
  */
 const CURLINFO_RETRY_AFTER = UNKNOWN;
+/**
+ * @var int
+ * @cvalue CURL_HTTP_VERSION_3
+ */
+const CURL_HTTP_VERSION_3  = UNKNOWN;
 #endif
 
 #if LIBCURL_VERSION_NUM >= 0x074300 /* Available since 7.67.0 */
@@ -3547,6 +3552,14 @@
 const CURLOPT_QUICK_EXIT = UNKNOWN;
 #endif
 
+#if LIBCURL_VERSION_NUM >= 0x075800 /* Available since 7.88.0 */
+/**
+ * @var int
+ * @cvalue CURL_HTTP_VERSION_3ONLY
+ */
+const CURL_HTTP_VERSION_3ONLY  = UNKNOWN;
+#endif
+
 /**
  * @var int
  * @cvalue CURLOPT_SAFE_UPLOAD