[SMSS] Use RTL string-safe functions in critical places. Add validity checks for returned NtQueryValueKey() data. (#2704)

- Not all the wcscpy() / swprintf() calls have been converted to their
  string-safe equivalents. Instead I used the string-safe functions only
  for places where strings of unknown length were copied into fixed-size
  internal buffers. On the contrary, for known-fixed-length strings being
  copied or numbers being converted to string representations in large
  enough buffers, I kept the original function calls.

- Verify the registry data that has been returned by NtQueryValueKey():
  * When expecting (not multi) strings, check whether the data type is
    either REG_SZ or REG_EXPAND_SZ.
  * When expecting DWORD values, check whether the data type is
    REG_DWORD and whether the data length is (greater or) equal to
    sizeof(ULONG).

base/system/smss/smsbapi.c

@@ -94,7 +94,7 @@ SmpSbCreateSession(IN PVOID Reserved,
                 NtClose(ProcessInformation->ProcessHandle);
                 NtClose(ProcessInformation->ThreadHandle);
                 SmpDereferenceSubsystem(KnownSubsys);
-                DbgPrint("SmpSbCreateSession: NtDuplicateObject (Thread) Failed %lx\n", Status);
+                DPRINT1("SmpSbCreateSession: NtDuplicateObject (Thread) Failed %lx\n", Status);
                 return Status;
             }