[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.

src/Protocol/OStatus.php

@@ -23,6 +23,7 @@ use Friendica\Network\Probe;
 use Friendica\Object\Image;
 use Friendica\Util\DateTimeFormat;
 use Friendica\Util\Network;
+use Friendica\Util\Proxy as ProxyUtils;
 use Friendica\Util\XML;
 
 require_once 'include/dba.php';
@@ -30,7 +31,6 @@ require_once 'include/items.php';
 require_once 'mod/share.php';
 require_once 'include/enotify.php';
 require_once 'include/api.php';
-require_once 'mod/proxy.php';
 
 /**
  * @brief This class contain functions for the OStatus protocol
@@ -1214,7 +1214,7 @@ class OStatus
 			}
 
 			// Is it a remote picture? Then make a smaller preview here
-			$preview = proxy_url($preview, false, PROXY_SIZE_SMALL);
+			$preview = ProxyUtils::proxifyUrl($preview, false, ProxyUtils::SIZE_SMALL);
 
 			// Is it a local picture? Then make it smaller here
 			$preview = str_replace(["-0.jpg", "-0.png"], ["-2.jpg", "-2.png"], $preview);