Feature: #108975 - Add Configuration Provider for Extbase Class Configuration 

See forge#108975

Description 

The Extbase class configuration (persistence mapping) is now exposed in the backend Configuration module (System > Configuration). The module is available when the system extension lowlevel is installed.

The displayed configuration reflects the configured mapping that Extbase uses at runtime: it is built by collecting and merging all Configuration/Extbase/Persistence/Classes.php definitions from active packages.

Impact 

This is a read-only usability improvement: developers and integrators can inspect and verify the resolved Extbase persistence class mapping (including extension overrides) directly in the backend, without dumping configuration arrays or manually checking each Configuration/Extbase/Persistence/Classes.php file.