configs/debug: add NET debug config

The debug.config file is really great to easily enable a bunch of
general debugging features on a CI-like setup. But it would be great to
also include core networking debugging config.

A few CI's validating features from the Net tree also enable a few other
debugging options on top of debug.config. A small selection is quite
generic for the whole net tree. They validate some assumptions in
different parts of the core net tree. As suggested by Jakub Kicinski in
[1], having them added to this debug.config file would help other CIs
using network features to find bugs in this area.

Note that the two REFCNT configs also select REF_TRACKER, which doesn't
seem to be an issue.

Link: https://lore.kernel.org/netdev/20240202093148.33bd2b14@kernel.org/T/ [1]
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20240212-kconfig-debug-enable-net-v1-1-fb026de8174c@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

kernel/configs/debug.config

@@ -40,6 +40,12 @@ CONFIG_UBSAN_ENUM=y
 CONFIG_UBSAN_SHIFT=y
 CONFIG_UBSAN_UNREACHABLE=y
 #
+# Networking Debugging
+#
+CONFIG_NET_DEV_REFCNT_TRACKER=y
+CONFIG_NET_NS_REFCNT_TRACKER=y
+CONFIG_DEBUG_NET=y
+#
 # Memory Debugging
 #
 # CONFIG_DEBUG_PAGEALLOC is not set