[TASK] Remove t3lib_install and t3lib_install_sql

* t3lib_install_sql was split from t3lib_install a while ago, the
non namespaced class is now cleaned up like the rest in t3lib/
* t3lib_install was not migrated since the methods in there were
obsoleted for 6.0 with the Configuration change. It was still
mentioned in dbal at some points, for example in a Hook for old em.
This is cleaned up along the way.