[WIP] Rewrite to Proxy class: (#5507)

* Rewrite to Proxy class:
- introduced new Friendica\Network\Proxy class for in exchange of proxy_*()
  functions
- moved also all PROXY_* constants there as Proxy::*
- removed now no longer needed mod/proxy.php loading as composer's auto-load
  will do this for us
- renamed those proxy_*() functions to better names:
  + proxy_init()           -> Proxy::init()         (public)
  + proxy_url()            -> Proxy::proxifyUrl()   (public)
  + proxy_parse_html()     -> Proxy::proxifyHtml()  (public)
  + proxy_is_local_image() -> Proxy::isLocalImage() (private)
  + proxy_parse_query()    -> Proxy::parseQuery()   (private)
  + proxy_img_cb()         -> Proxy::replaceUrl()   (private)

* Ops, need to set $a here ...

* CR request:
- moved Proxy class to Friendica\Module
- extended BaseModule

* Ops, no need for own instance of $a when self::getApp() is around.

* Proxy-rewrite:
- proxy_url() and proxy_parse_html() are both non-module functions (now
  methods)
- so they must be splitted into a seperate class
- also the SIZE_* and DEFAULT_TIME constants are both not relevant to module

* No instances from utility classes

* Fixed error:
- proxify*() is now located in `Friendica\Util\ProxyUtils`

* Moved back to original place, ops? How did they move here? Well, it was not
intended by me.

* Removed duplicate (left-over from split) constants and static array. Thank to
MrPetovan finding it.

* Renamed ProxyUtils -> Proxy and aliased it back to ProxyUtils.

include/api.php

@@ -40,6 +40,7 @@ use Friendica\Object\Image;
 use Friendica\Protocol\Diaspora;
 use Friendica\Util\DateTimeFormat;
 use Friendica\Util\Network;
+use Friendica\Util\Proxy as ProxyUtils;
 use Friendica\Util\XML;
 
 require_once 'include/conversation.php';
@@ -47,7 +48,6 @@ require_once 'mod/share.php';
 require_once 'mod/item.php';
 require_once 'include/security.php';
 require_once 'mod/wall_upload.php';
-require_once 'mod/proxy.php';
 
 define('API_METHOD_ANY', '*');
 define('API_METHOD_GET', 'GET');
@@ -2518,7 +2518,7 @@ function api_get_entitities(&$text, $bbcode)
 		preg_match_all("/\[img](.*?)\[\/img\]/ism", $bbcode, $images);
 
 		foreach ($images[1] as $image) {
-			$replace = proxy_url($image);
+			$replace = ProxyUtils::proxifyUrl($image);
 			$text = str_replace($image, $replace, $text);
 		}
 		return [];
@@ -2627,7 +2627,7 @@ function api_get_entitities(&$text, $bbcode)
 				// If image cache is activated, then use the following sizes:
 				// thumb  (150), small (340), medium (600) and large (1024)
 				if (!Config::get("system", "proxy_disabled")) {
-					$media_url = proxy_url($url);
+					$media_url = ProxyUtils::proxifyUrl($url);
 
 					$sizes = [];
 					$scale = Image::getScalingDimensions($image[0], $image[1], 150);