General moving to keep kernel object types separate from the direct
kernel code. Also essentially a preliminary cleanup before eliminating
global kernel state in the kernel code.
Sessions and Ports are now detached from each other.
HLE services are handled by means of a SessionRequestHandler class, Interface now inherits from this class.
The File and Directory classes are no longer kernel objects, but SessionRequestHandlers instead, bound to a ServerSession when requested.
File::OpenLinkFile now creates a new session pair and binds the File instance to it.
All handles obtained via srv::GetServiceHandle or svcConnectToPort are references to ClientSessions.
Service modules will wait on the counterpart of those ClientSessions (Called ServerSessions) using svcReplyAndReceive or svcWaitSynchronization[1|N], and will be awoken when a SyncRequest is performed.
HLE Interfaces are now ClientPorts which override the HandleSyncRequest virtual member function to perform command handling immediately.
