split out mkSharedMemoryRequestPortal

Change-Id: I6fd13a9205d1f72a121dbf4e890f340c9d2b1173
pass in a particular read/write server to mkSharedMemoryRequestPortal

Change-Id: I42b49bdfeaa5de76c9df67aca47e0ee80db0bc91
moved SharedMemoryPortal to lib/bsv

Change-Id: I3f2cf4631fa3e5cc6c1f50c3a0cb668c4f88e09e