Alert transport cleanup, no_proxy support and other proxy cleanups (#14763)

* Add no_proxy and other proxy related settings
Set user agent on all http client requests
Unify http client usage

* Style fixes

* Remove useless use statements

* Correct variable, good job phpstan

* Add tests
fix https_proxy bug
add tcp:// to the config settings format

* style and lint fixes

* Remove guzzle from the direct dependencies

* Use built in Laravel testing functionality

* update baseline

phpstan-baseline.neon

@@ -1,10 +1,5 @@
 parameters:
 	ignoreErrors:
-		-
-			message: "#^Static property LibreNMS\\\\Alert\\\\Transport\\\\Sensu\\:\\:\\$severity is never read, only written\\.$#"
-			count: 1
-			path: LibreNMS/Alert/Transport/Sensu.php
-
 		-
 			message: "#^If condition is always false\\.$#"
 			count: 1