PHPC-1835: Rotate credentials for Atlas connectivity tests

This corresponds with a change to the project's Evergreen config to rotate keys for decrypting atlas-uris.txt.enc.

Additionally, this adds comments atlas-uris.txt and atlas.phpt test output for improved readability.

Author: jmikola

.evergreen/atlas-uris.txt.enc

@@ -15,10 +15,16 @@ $query = new \MongoDB\Driver\Query([]);
 
 foreach ($urls as $url) {
 	$url = trim($url);
+
 	if ($url == '') {
 		continue;
 	}
 
+	if (strpos($url, '#') === 0) {
+		echo trim(substr($url, 1)), "\n";
+		continue;
+	}
+
 	try {
 		$m = new \MongoDB\Driver\Manager($url);
 		$m->executeCommand('admin', $command);
@@ -32,16 +38,22 @@ foreach ($urls as $url) {
 ===DONE===
 <?php exit(0); ?>
 --EXPECTF--
+Atlas replica set (3.4)
 PASS
 PASS
+Atlas sharded cluster (3.4)
 PASS
 PASS
+Atlas free tier replica set (4.4)
 PASS
 PASS
+Atlas with only TLSv1.1 enabled (3.4)
 PASS
 PASS
+Atlas with only TLSv1.2 enabled (3.4)
 PASS
 PASS
+Atlas with only TLSv1.2 enabled (3.4) and bad credentials
 FAIL: %s
 FAIL: %s
 ===DONE===