Use --EXTENSIONS-- section for newly added tests

As of PHP 8.1.0, the `--EXTENSIONS-- section is properly supported, and
CIs may make use of that (our AppVeyor CI does).  Thus it is important
to list required extensions there, since otherwise they may not be
loaded, causing the test to be skipped, or worse, to be borked.

Author: cmb69

ext/mysqli/tests/gh9590.phpt

@@ -1,9 +1,9 @@
 --TEST--
 Bug GH-9602 (stream_select does not abort upon exception or empty valid fd set)
+--EXTENSIONS--
+mysqli
 --SKIPIF--
 <?php
-require_once('skipif.inc');
-require_once('connect.inc');
 require_once('skipifconnectfailure.inc');
 
 if (!$IS_MYSQLND)

ext/standard/tests/streams/gh9590-001.phpt

@@ -1,5 +1,7 @@
 --TEST--
 Bug GH-9590 001 (stream_select does not abort upon exception or empty valid fd set)
+--EXTENSIONS--
+posix
 --SKIPIF--
 <?php
 if (!function_exists('posix_setrlimit') || !posix_setrlimit(POSIX_RLIMIT_NOFILE, 2048, -1)) {

ext/standard/tests/streams/gh9590-002.phpt

@@ -1,5 +1,7 @@
 --TEST--
 Bug GH-9590 002 (stream_select does not abort upon exception or empty valid fd set)
+--EXTENSIONS--
+posix
 --SKIPIF--
 <?php
 if (!function_exists('posix_setrlimit') || !posix_setrlimit(POSIX_RLIMIT_NOFILE, 2048, -1)) {