Phan: Add phan deps and cli wrapper (#36333)

Per pdWQjU-IH-p2, we're going to use Phan for PHP static analysis.

This commit adds the phan composer deps and a wrapper for the Jetpack
CLI.

It also adds the php-ast extension inside the Docker env, and adds some
docs about running Phan.

---------

Co-authored-by: Igor Zinovyev <[email protected]>
Co-authored-by: Steve D <[email protected]>
Co-authored-by: Samiff <[email protected]>

Author: 4 people

.github/workflows/linting.yml

@@ -189,7 +189,7 @@ jobs:
           composer install --ignore-platform-reqs
           # Remove stuff we don't need here that fails some platform reqs.
           # This will complain if we missed any.
-          composer remove --dev sirbrillig/phpcs-changed automattic/jetpack-codesniffer
+          composer remove --dev sirbrillig/phpcs-changed automattic/jetpack-codesniffer phan/phan
 
       - name: Run linter
         run: |

composer.json

@@ -11,7 +11,11 @@
 		"automattic/jetpack-codesniffer": "@dev",
 		"automattic/jetpack-phpcs-filter": "@dev",
 		"dealerdirect/phpcodesniffer-composer-installer": "1.0.0",
+		"phan/phan": "^5.4",
 		"php-parallel-lint/php-parallel-lint": "1.3.2",
+		"php-stubs/wordpress-stubs": "^6.4.3",
+		"php-stubs/wordpress-tests-stubs": "^6.3",
+		"php-stubs/wp-cli-stubs": "^2.10",
 		"sirbrillig/phpcs-changed": "2.11.4",
 		"squizlabs/php_codesniffer": "^3.6.2"
 	},