wireguard-tools: use kconfig dependency for ip instead of runtime

wireguard-tools: use kconfig dependency for ip instead of runtime

The conditional runtime dependency on the ip package was originally
intended to only pull in the ip package when busybox ip is not
configured. However, in APK-based builds the BUSYBOX_CONFIG_*
variables may not be resolvable at package metadata generation
time, causing the ip dependency to be unconditionally baked into
the .apk package. This forces users to install ip-tiny or ip-full
even though busybox already provides the ip command.

Revert to the previous +@BUSYBOX_CONFIG_IP / +@BUSYBOX_CONFIG_FEATURE_IP_LINK
kconfig-level dependencies. These ensure busybox ip support is
enabled at config time without creating a runtime package dependency.
Both options default to y, and wireguard.uc only uses basic
ip link commands that busybox fully supports.

Fixes: openwrt#22637
Signed-off-by: Anand Kumar <anandvtu16158@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/22652
Signed-off-by: Robert Marko <robimarko@gmail.com>