gdb: make store_integer take an array_view

Change store_integer, store_signed_integer and store_unsigned_integer to
accept an array_view.  Add some backwards compatibility overloads to
avoid changing all callers at once.

Change-Id: Ibb1381228ab1cb65fc7e2e4b92cf9ab1047cdc03
Reviewed-By: John Baldwin <jhb@FreeBSD.org>