Add hooks subnode to Stmt\Property and Param, which contains an
array of PropertyHook.
The property hook support is considered experimental and subject
to change.
RFC: https://wiki.php.net/rfc/property-hooks
Adds support for PHP 8 attributes, represented using `AttrGroup` nodes
containing `Attribute` nodes. The `attrGroup` subnode is added to all
nodes that can have attributes.
This is still missing FPPP support.
Co-authored-by: Nikita Popov <nikita.ppv@gmail.com>