Deprecation: #95800 - Deprecate generating public URL for private asset files

See Issue #95800

Description

Since TYPO3 6, extensions have been restructured to have public asset files in Resources/Public folder only.

Unfortunately having public assets in extensions located in other folders never was deprecated. This is now done.

Impact

Public assets of extensions (files that should be delivered by the web server) MUST be located in Resources/Public folder of the extension, otherwise a deprecation message is now emitted once a URL to such asset is resolved.

Affected Installations

Installations having extensions activated, that have public asset files in other locations than Resources/Public.

Migration

Extension authors should move all public assets to Resources/Public folder