PHPStan level 9 (#229)

* PHPStan level 9

* Update src/Media_Command.php

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Update src/Media_Command.php

* Update src/Media_Command.php

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Update src/Media_Command.php

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Update src/Media_Command.php

* More fixes

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: swissspidy

phpstan.neon.dist

@@ -0,0 +1,12 @@
+parameters:
+  level: 9
+  paths:
+    - src
+    - media-command.php
+  scanDirectories:
+    - vendor/wp-cli/wp-cli/php
+  scanFiles:
+    - vendor/php-stubs/wordpress-stubs/wordpress-stubs.php
+  treatPhpDocTypesAsCertain: false
+  ignoreErrors:
+    - identifier: missingType.iterableValue