event: harden APIs that accept arrays

plugin devs can't be relied on to pass the proper types to these APIs, and when the wrong types get passed it makes type errors appear from inside the internals.

tests/phpstan/configs/phpstan-bugs.neon

@@ -35,6 +35,11 @@ parameters:
 			count: 1
 			path: ../../../src/pocketmine/utils/Utils.php
 
+		-
+			message: "#^Parameter \\#1 \\$ of closure expects TMemberType, TMemberType given\\.$#"
+			count: 1
+			path: ../../../src/pocketmine/utils/Utils.php
+
 		-
 			message: "#^Call to static method PHPUnit\\\\Framework\\\\Assert\\:\\:assertNotNull\\(\\) with int and string will always evaluate to true\\.$#"
 			count: 1