Cleanup pass based on prior PRs (#21)

* Updates to stub generation

* More idiomatic fixes from PHP team

* Moved tests from src/tests -> tests, got rid of extension-only tests

* fixed up test paths, regenerated arginfo

ext/awscrt.stub.php

@@ -1,6 +1,9 @@
 <?php
 
-/** @generate-class-entries */
+/**
+ * @generate-class-entries
+ * @generate-function-entries
+*/
 
 function aws_crt_last_error(): int {}