MC-30776: Improve Performance of SVC

- Added nikic/php-parser as hard dependency in composer
- Improved performance of DependencyMap creation.
- Remove stms when adding ClassMethod nodes to dependency tree
- Added better doc comments
- Addeed more aggresive AbstractApiVisitor traversal termination
- Refactored code to use switch statements

Author: Rrego6

composer.json

@@ -13,7 +13,8 @@
         "symfony/console": "~4.1.0||~4.4.0",
         "tomzx/php-semver-checker": "^0.13.0",
         "wikimedia/less.php": "~1.8.0",
-        "zendframework/zend-stdlib": "^3.2.1"
+        "zendframework/zend-stdlib": "^3.2.1",
+        "nikic/php-parser": "^3.1"
     },
     "require-dev": {
         "phpunit/phpunit": "^6.5.0",