kconfig: nconf: Add search jump feature

Menuconfig has a feature where you can "press the key in the (#) prefix
to jump directly to that location. You will be returned to the current
search results after exiting this new menu."

This commit adds this feature to nconfig, with almost identical code.

Signed-off-by: Jesse Taube <Mr.Bossman075@gmail.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>