Get rid of the complicated New Free Tree module

[m-stein]

The module currently used for the allocation of Physical Block Addresses on Copy-On-Write in the Virtual Block Device is called New Free Tree module. Unfortunately, this module's implementation ignores the module design of the CBE at some points and uses an approach with an abstraction of stacks of tree nodes that is hard to understand and adapt. I want to get rid of the somewhat superfluous and obstructive stack abstraction and concentrate the core logic of the module to the call of the Execute procedure (as with most of the modules). With the Free Tree Resizing module, there exists already a design-conforme base for this work that brings most of the state required for parsing the Free Tree. So, my approach is to move the allocation operation to this module and then remove the New Free Tree module from the CBE.

This change is a preparation for a systematic optimization of how the Free Tree module allocates blocks.