kernel/svc: Implement svcGetProcessList

This service function simply copies out a specified number of kernel
process IDs, while simultaneously reporting the total number of
processes.

src/core/hle/kernel/kernel.h

@@ -72,6 +72,9 @@ public:
     /// Retrieves a const pointer to the current process.
     const Process* CurrentProcess() const;
 
+    /// Retrieves the list of processes.
+    const std::vector<SharedPtr<Process>>& GetProcessList() const;
+
     /// Adds a port to the named port table
     void AddNamedPort(std::string name, SharedPtr<ClientPort> port);