Display active configuration / override files when loading content

Currently RetroArch loads global configuration files, core overrides, directory overrides and game overrides silently.
While this is technically correct, it makes troubleshooting input and configuration issues unnecessarily difficult.

Proposed feature:
Display a short overlay on-screen notification when content is loaded, indicating which configuration files are active.
Example:

Loaded configuration:

• retroarch.cfg
• puae-core.cfg
• lotus_esprit_turbo_challenge.cfg

This could be shown briefly as an overlay (similar to controller connection messages) or logged clearly in the frontend log.

Use case:
This would significantly improve usability when dealing with:
multiple controllers
identical controller models
core-specific input behavior
unexpected overrides
Users could immediately identify whether an issue originates from global settings, a core override or a game-specific configuration.

Benefit:
Better transparency
Faster troubleshooting
No functional change to existing behavior
Especially helpful for advanced users and debugging scenarios

Trace the content-loading path where global configuration, core overrides, directory overrides, and game overrides are applied. Compare the existing controller connection overlay notifications with frontend logging, then define whether the active filenames appear briefly on screen or clearly in the log; done means the loaded configuration list is visible for each content load without changing behavior.