Move tests for sendBeacon to a separate dedicated directory for clearer ownership

third_party/WebKit/LayoutTests/http/tests/navigation/resources/check-beacon.php

-<?php
-require_once '../../resources/portabilityLayer.php';
-
-$beaconFilename = sys_get_temp_dir() . "/beacon" . (isset($_REQUEST['name']) ? $_REQUEST['name'] : "") . ".txt";
-
-$max_attempts = 700;
-$retries = isset($_REQUEST['retries']) ? (int)$_REQUEST['retries'] : $max_attempts;
-while (!file_exists($beaconFilename) && $retries != 0) {
-    usleep(10000);
-    # file_exists() caches results, we want to invalidate the cache.
-    clearstatcache();
-    $retries--;
-}
-
-header('Content-Type: text/plain');
-header('Access-Control-Allow-Origin: *');
-if (file_exists($beaconFilename)) {
-    $beaconFile = false;
-    if (is_readable($beaconFilename)) {
-        $beaconFile = fopen($beaconFilename, 'r');
-    }
-    if ($beaconFile) {
-        echo "Beacon sent successfully\n";
-        while ($line = fgets($beaconFile)) {
-            $trimmed = trim($line);
-            if ($trimmed != "")
-                echo "$trimmed\n";
-        }
-        fclose($beaconFile);
-        unlink($beaconFilename);
-    } else {
-        echo "Beacon status not readable\n";
-    }
-} else {
-    echo "Beacon not sent\n";
-}
-?>