feat(legacy): consolidate constants (#1558)

* remove unused file

* fix paths leading slash

* remove useless imports

* refactor(legacy): use constants everywhere

* fix path leading slash

* remove useless import

* consolidate legacy contants

* format code

* reuse LIBRETIME_CONFIG_DIR

* fix test config path

* remove ci legacy log dir creation

* some logs improvements

legacy/application/cloud_storage/ProxyStorageBackend.php

@@ -17,7 +17,7 @@ class ProxyStorageBackend extends StorageBackend
     {
         $CC_CONFIG = Config::getConfig();
 
-        // The storage backend in the airtime.conf directly corresponds to
+        // The storage backend in the config file directly corresponds to
         // the name of the class that implements it, so we can create the
         // right backend object dynamically:
         if ($storageBackend == 'file') {