Make unrepeatable tests retriable

This was an error in thinking on my side. The reason these tests are
unrepeatable is because --repeat executes the same request in the same process,
and does not run the CLEAN section in between runs. This is not the case when
retrying tests.

We could potentially make CLEAN tests repeatable by including the CLEAN section
in the tested script. This does however not work for all tests (e.g. tests that
set open_basedir).

Closes GH-12072

run-tests.php

@@ -1886,7 +1886,6 @@ function run_test(string $php, $file, array $env): string
         $skipCache = new SkipCache($enableSkipCache, $cfg['keep']['skip']);
     }
 
-    $retriable = true;
     $retried = false;
 retry:
 
@@ -1935,7 +1934,6 @@ function run_test(string $php, $file, array $env): string
     $tested = $test->getName();
 
     if ($test->hasSection('FILE_EXTERNAL')) {
-        $retriable = false;
         if ($num_repeats > 1) {
             return skip_test($tested, $tested_file, $shortname, 'Test with FILE_EXTERNAL might not be repeatable');
         }
@@ -1964,7 +1962,6 @@ function run_test(string $php, $file, array $env): string
         }
         $php = $php_cgi . ' -C ';
         $uses_cgi = true;
-        $retriable = false;
         if ($num_repeats > 1) {
             return skip_test($tested, $tested_file, $shortname, 'CGI does not support --repeat');
         }
@@ -1982,15 +1979,13 @@ function run_test(string $php, $file, array $env): string
         } else {
             return skip_test($tested, $tested_file, $shortname, 'phpdbg not available');
         }
-        $retriable = false;
         if ($num_repeats > 1) {
             return skip_test($tested, $tested_file, $shortname, 'phpdbg does not support --repeat');
         }
     }
 
     foreach (['CLEAN', 'STDIN', 'CAPTURE_STDIO'] as $section) {
         if ($test->hasSection($section)) {
-            $retriable = false;
             if ($num_repeats > 1) {
                 return skip_test($tested, $tested_file, $shortname, "Test with $section might not be repeatable");
             }
@@ -2173,7 +2168,6 @@ function run_test(string $php, $file, array $env): string
         settings2array(preg_split("/[\n\r]+/", $ini), $ini_settings);
 
         if (isset($ini_settings['opcache.opt_debug_level'])) {
-            $retriable = false;
             if ($num_repeats > 1) {
                 return skip_test($tested, $tested_file, $shortname, 'opt_debug_level tests are not repeatable');
             }
@@ -2747,7 +2741,7 @@ function run_test(string $php, $file, array $env): string
 
         $wanted_re = null;
     }
-    if (!$passed && !$retried && $retriable && error_may_be_retried($test, $output)) {
+    if (!$passed && !$retried && error_may_be_retried($test, $output)) {
         $retried = true;
         goto retry;
     }