[5.1] Switching Folder::files() to framework version

[Hackwar]

Summary of Changes

The CMS filesystem package has been deprecated for some time now and is supposed to be removed in 6.0. This PR removes some of the dependencies of the CMS on the Folder class and switches that dependency to the framework class. So far this only switches calls to Folder::files() to the framework package. Where additional methods are called from the package, I didn't change it.

Testing Instructions

Codereview.

#40131 is another PR related to this effort.

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

[Fedik]

I have tested this item ✅ successfully on b94e597

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[bembelimen]

Thx