pgl: begin skeletoning shell service, implement two commands.

libraries/libstratosphere/source/pm/pm_shell_api.cpp

@@ -24,4 +24,8 @@ namespace ams::pm::shell {
         return pmshellLaunchProgram(launch_flags, reinterpret_cast<const NcmProgramLocation *>(&loc), reinterpret_cast<u64 *>(out_process_id));
     }
 
+    Result TerminateProcess(os::ProcessId process_id) {
+        return ::pmshellTerminateProcess(static_cast<u64>(process_id));
+    }
+
 }