HV:Remove i/o session sw interface from hypervisor shell

to remove it as no requirement of bounding i/o handlers
  dynamically in hypervisor shell

  - update source code related with i/o session

  - move shell command definitions from shell_pulic.c
    to shell_internal.c

  - remove shell_public.c

Signed-off-by: Yonghua Huang <yonghua.huang@intel.com>
Reviewed-by: Jason Chen CJ <jason.cj.chen@intel.com>
Acked-by: Eddie Dong <eddie.dong@intel.com>

hypervisor/debug/vuart.c

@@ -330,7 +330,8 @@ void vuart_console_rx_chars(struct vuart *vu)
 
 	if (ch == GUEST_CONSOLE_TO_HV_SWITCH_KEY) {
 		/* Switch the console */
-		shell_switch_console();
+		vu->active = false;
+		printf("\r\n\r\n ---Entering ACRN SHELL---\r\n");
 	}
 	if (ch != -1) {
 		fifo_putchar(&vu->rxfifo, ch);