Feature: #96659 - ContentObject Registration via service configuration

See forge#96659

Description

ContentObjects such as TEXT or COA for rendering content blocks in TYPO3 Frontend via TypoScript are now registered via the service configuration.

This way registration is done during build-time and not on every TYPO3 request and dependency injection can be used in ContentObjects.

The registration was previously done in an extension's ext_localconf.php via $GLOBALS['TYPO3_CONF_VARS']['FE']['ContentObjects'].

Impact

Registering a custom ContentObject is now done in an extension's Configuration/Services.yaml:

MyCompany\MyPackage\ContentObject\CustomContentObject:
    tags:
        - name: frontend.contentobject
          identifier: 'MY_OBJ'