[idd] ipc: connect LGInput to LGIdd

Move the reusable named-pipe endpoint and shared support code into
the LGCommon static library.

Run a dedicated server in LGIdd and a reconnecting client in
LGInput, with device-lifecycle handling and report framing.

Refactor the helper pipe to use the same endpoint implementation.

idd/LGCommon/PipeMsg.h

@@ -22,7 +22,7 @@
 
 #include <stdint.h>
 
-#define LG_PIPE_NAME "\\\\.\\pipe\\LookingGlassIDD"
+static constexpr wchar_t LG_PIPE_NAME[] = L"\\\\.\\pipe\\LookingGlassIDD";
 
 struct LGPipeMsg
 {
@@ -68,3 +68,5 @@ struct LGPipeMsg
     resolutionRejected;
   };
 };
+
+static_assert(sizeof(LGPipeMsg) == 20, "LGPipeMsg wire layout changed");