[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/Content/Text/BBCode.php

@@ -24,10 +24,9 @@ use Friendica\Object\Image;
 use Friendica\Util\Map;
 use Friendica\Util\Network;
 use Friendica\Util\ParseUrl;
+use Friendica\Util\Proxy as ProxyUtils;
 use League\HTMLToMarkdown\HtmlConverter;
 
-require_once "mod/proxy.php";
-
 class BBCode extends BaseObject
 {
 	/**
@@ -361,7 +360,7 @@ class BBCode extends BaseObject
 	{
 		// Only send proxied pictures to API and for internal display
 		if (in_array($simplehtml, [false, 2])) {
-			return proxy_url($image);
+			return ProxyUtils::proxifyUrl($image);
 		} else {
 			return $image;
 		}
@@ -1033,7 +1032,7 @@ class BBCode extends BaseObject
 				} else {
 					$text = trim($share[1]) . "\n";
 
-					$avatar = proxy_url($avatar, false, PROXY_SIZE_THUMB);
+					$avatar = ProxyUtils::proxifyUrl($avatar, false, ProxyUtils::SIZE_THUMB);
 
 					$tpl = get_markup_template('shared_content.tpl');
 					$text .= replace_macros($tpl, [