frr: enable frr-vtysh by defalult and hide it

Fixes [1]
lib/vty.c: In function 'vty_mgmt_resume_response':
lib/vty.c:195:27: error: 'VTYSH_READ' undeclared (first use in this function); did you mean 'VTY_READ'?
  195 |                 vty_event(VTYSH_READ, vty);
      |                           ^~~~~~~~~~
      |                           VTY_READ

The error is a bug in frr: not all use cases of the VTYSH_* enums are
guarded by #ifdef VTYSH. These enums are enabled by the VTYSH macro,
which is defined if sub package frr-vtysh is enabled in menuconfig.
According to support ticket [2], building without frr-vtysh is
no longer supported.

[1] openwrt#24063
[2] FRRouting/frr#15752 (comment)

Signed-off-by: Georgi Valkov <gvalkov@gmail.com>

net/frr/Makefile

@@ -8,7 +8,7 @@
 include $(TOPDIR)/rules.mk
 PKG_NAME:=frr
 PKG_VERSION:=9.0.0
-PKG_RELEASE:=2
+PKG_RELEASE:=3
 PKG_SOURCE_DATE:=2023-08-12
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_SOURCE_DATE).tar.gz
@@ -106,6 +106,8 @@ define Package/frr-vtysh
   DEPENDS+=+frr-libfrr +libreadline +libncurses +more
   TITLE:=integrated shell for frr routing software
   CONFLICTS:=quagga-vtysh
+  DEFAULT:=y if PACKAGE_frr
+  HIDDEN:=1
 endef
 
 define Package/frr-watchfrr