[zion] Move the final syscalls to the new format.

zion/syscall/capability.cpp

@@ -0,0 +1,13 @@
+#include "syscall/capability.h"
+
+#include "scheduler/scheduler.h"
+
+z_err_t CapDuplicate(ZCapDuplicateReq* req) {
+  auto& proc = gScheduler->CurrentProcess();
+  auto cap = proc.GetCapability(req->cap_in);
+  if (!cap) {
+    return Z_ERR_CAP_NOT_FOUND;
+  }
+  *req->cap_out = proc.AddExistingCapability(cap);
+  return Z_OK;
+}