This is a simplication of the asyncronous-IPC module of the base-hw kernel.
Besides structuring the code in a cleaner way, it prepares for the in-place
translation of the module into Ada in the context of the Spunky project.
* Get rid of virtual methods in Ipc_node.
* Move all stuff related to protection domains, capabilities, and UTCBs to
the Thread class. this code might later be moved to a dedicated module, but
for now it's just fine to have it done by the thread module.
Ref #3308
6a5aa18a7b