Enable PHPStan Level 6 (#1194)

* Update phpstan.neon

* Update YandexTest.php

* Update TomTomTest.php

* Update PickPointTest.php

* Update PickPoint.php

* Update PhotonTest.php

* Update PeliasTest.php

* Update OpenRouteServiceTest.php

* Update OpenCageTest.php

* Update OpenCage.php

* Update NominatimTest.php

* Update MaxMindBinaryTest.php

* Update MaxMindTest.php

* [WIP] Apply PHPStan fixes

* Apply PHPCSFixer fixes

* [WIP] Apply PHPStan fixes

* [WIP] Apply PHPStan fixes

* Revert "[WIP] Apply PHPStan fixes"

This reverts commit 734c5c52fbcba4bc12cbda07b58d902a79d47891.

* [WIP] Apply PHPStan fixes

* [WIP] Apply PHPStan fixes

* Update phpstan-baseline.neon

Tests/Provider/AbstractHttpProviderTest.php

@@ -23,7 +23,7 @@
 
 class AbstractHttpProviderTest extends TestCase
 {
-    public function testHttpClientGetter()
+    public function testHttpClientGetter(): void
     {
         $client = $this->getMockBuilder(Client::class)->disableOriginalConstructor()->getMock();
         $provider = new DummyProvider($client);