[TASK] Raise PHPStan to level 4 (#1254)

The higher level creates new warnings which I will address in
a separate change.

Part of #1252

phpstan-baseline.neon

@@ -1,2 +1,21 @@
 parameters:
-	ignoreErrors: []
+	ignoreErrors:
+		-
+			message: "#^Call to static method PHPUnit\\\\Framework\\\\Assert\\:\\:assertInstanceOf\\(\\) with 'TYPO3\\\\\\\\CMS\\\\\\\\Extbase\\\\\\\\Mvc\\\\\\\\Controller\\\\\\\\ActionController' and PHPUnit\\\\Framework\\\\MockObject\\\\MockObject&TTN\\\\Tea\\\\Controller\\\\FrontEndEditorController&TYPO3\\\\TestingFramework\\\\Core\\\\AccessibleObjectInterface will always evaluate to true\\.$#"
+			count: 1
+			path: Tests/Unit/Controller/FrontEndEditorControllerTest.php
+
+		-
+			message: "#^Call to static method PHPUnit\\\\Framework\\\\Assert\\:\\:assertInstanceOf\\(\\) with 'TYPO3\\\\\\\\CMS\\\\\\\\Extbase\\\\\\\\Mvc\\\\\\\\Controller\\\\\\\\ActionController' and PHPUnit\\\\Framework\\\\MockObject\\\\MockObject&TTN\\\\Tea\\\\Controller\\\\TeaController&TYPO3\\\\TestingFramework\\\\Core\\\\AccessibleObjectInterface will always evaluate to true\\.$#"
+			count: 1
+			path: Tests/Unit/Controller/TeaControllerTest.php
+
+		-
+			message: "#^Call to static method PHPUnit\\\\Framework\\\\Assert\\:\\:assertInstanceOf\\(\\) with 'TYPO3\\\\\\\\CMS\\\\\\\\Extbase\\\\\\\\DomainObject\\\\\\\\AbstractEntity' and TTN\\\\Tea\\\\Domain\\\\Model\\\\Tea will always evaluate to true\\.$#"
+			count: 1
+			path: Tests/Unit/Domain/Model/TeaTest.php
+
+		-
+			message: "#^Call to static method PHPUnit\\\\Framework\\\\Assert\\:\\:assertInstanceOf\\(\\) with 'TYPO3\\\\\\\\CMS\\\\\\\\Extbase\\\\\\\\Persistence\\\\\\\\Repository' and TTN\\\\Tea\\\\Domain\\\\Repository\\\\TeaRepository will always evaluate to true\\.$#"
+			count: 1
+			path: Tests/Unit/Domain/Repository/TeaRepositoryTest.php

phpstan.neon

@@ -10,7 +10,7 @@ parameters:
     # Don't be overly greedy on machines with more CPU's to be a good neighbor especially on CI
     maximumNumberOfProcesses: 5
 
-  level: 3
+  level: 4
 
   bootstrapFiles:
     - .Build/vendor/autoload.php