keep a list of file handles open per session

- Track open SFTP file handles per session in a fileList, returning
  opaque session-scoped handle IDs instead of raw file descriptors.
- Resolve and validate client-supplied handle IDs via FindFileHandle.
- Free the handle list and close handles on error paths, including the
  Windows code paths.
- Drop the old raw-fd SFTP_ValidateFileHandle/STOREHANDLE handle table
  and its tests, superseded by the per-session ID lookup.

Author: JacobBarthelmeh

ide/Renesas/e2studio/RX72N/wolfssh_RX72N/wolfssh_user_setting.h

@@ -35,7 +35,6 @@
 #define WOLFSSH_NO_TIMESTAMP
 
 #define WOLFSSH_FATFS
-#define WOLFSSH_STOREHANDLE
 #define PRINTF printf
 #define DEFAULT_WINDOW_SZ 16384
 #define WOLFSSH_NO_RSA