The installer for components and plugins already automatically delete files, which are no longer present in the extension manifest. The module installer doesn't do that for some reason.
This PR proposes to add this functionality as I think it's a helpful feature for extension developers. Otherwise one has to manage a script file to delete no longer used files.

Summary of Changes

Added a property to track old installed files for updates.
This allows the parseFiles() method to automatically remove deleted files.
The Same code is already used in plugin and component adapter.

Testing Instructions

Install a module which used to have a file or folder that got deleted. Make sure it's an update (the module was already installed before).
You can fake such a module by taking any module and remove a file or folder line in the manifest and then install it.

Actual result BEFORE applying this Pull Request

The removed files or folder in the manifest are still present on the webserver after the update

Expected result AFTER applying this Pull Request

The removed files or folder in the manifest are deleted on the webserver after the update

Link to documentations

Please select:

• Documentation link for docs.joomla.org:

• No documentation changes for docs.joomla.org needed

• Pull Request link for manual.joomla.org:

• No documentation changes for manual.joomla.org needed