Remove support for TYPO3 v12

[brotkrueml]

For now, this is just a collection of tasks to be done once compatibility for TYPO3 v12 is removed.

• Class AddBreadcrumbList: remove 255 (recycler) from DEFAULT_DOKTYPES_TO_EXCLUDE constant (also mentioning in extension configuration), also in test
• Register event listeners via PHP attribute (changelog)
• Remove compatibility with Symfony 6.4 in composer.json
• Remove addRootLineFields condition in ext_localconf.php
• Remove compatibility with testing-framework v8