Feature: #94692 - Registering Icons via Service Container

Description

Extensions can now register their custom icons via a configuration file placed in Configuration/Icons.php of their extension directory, e.g. typo3conf/ext/my_extension/Configuration/Icons.php.

Each file needs to return a flat PHP configuration array, with custom options used for the IconRegistry to register a new icon.

Example:

<?php
return [
    'myicon' => [
        'provider' => \TYPO3\CMS\Core\Imaging\IconProvider\SvgIconProvider::class,
        'source' => 'EXT:my_extension/Resources/Public/Icons/myicon.svg'
    ],
    'anothericon' => [
        'provider' => \TYPO3\CMS\Core\Imaging\IconProvider\SvgIconProvider::class,
        'source' => 'EXT:my_extension/Resources/Public/Icons/anothericon.svg'
    ],
    ...
];

Impact

Using the new approach improves the loading speed of every request as the registration can be handled at once and cached during warmup of the core caches.

In addition, extension authors' ext_localconf.php files are drastically reduced, as extension authors have a better overview and a better separation of concerns when registering custom functionality.