Breaking: #67027 - Removed FLOW-compatibility from PackageManager
See forge#67027
Description
The Package Manager has been simplified and trimmed down to fit the needs of the TYPO3 extensions and typical Composer packages. All shipped code backported from Flow was removed or refactored to be included in the TYPO3 Core natively. Loading classes are done with the Composer class loader or by the conventions of extension namings. All default Composer packages can still be included as usual, however the custom Flow-logic has been removed.
Impact
It is not possible to add custom Package.php loaders into TYPO3 extensions anymore to be called during runtime. It is
not possible to configure extensions with custom Classes/ directories and custom composer.json locations anymore.
There is no special handling for "typo3-flow" packages anymore. The typo3conf/ file now only
contains the parts that are necessary for the TYPO3 system.
Affected Installations
All installations using custom functionality of the PackageManager not in use with the TYPO3 Core, or installations trying to use Flow packages natively in the TYPO3 Core.
Migration
Use Composer packages natively for class loading, or use ext_localconf.php to additionally configure a package.