netlink: support all extack types in dumps

Note that when this commit message refers to netlink dump
it only means the actual dumping part, the parsing / dump
start is handled by the same code as "doit".

Commit 4a19edb6 ("netlink: Pass extack to dump handlers")
added support for returning extack messages from dump handlers,
but left out other extack info, e.g. bad attribute.

This used to be fine because until YNL we had little practical
use for the machine readable attributes, and only messages were
used in practice.

YNL flips the preference 180 degrees, it's now much more useful
to point to a bad attr with NL_SET_BAD_ATTR() than type
an English message saying "attribute XYZ is $reason-why-bad".

Support all of extack. The fact that extack only gets added if
it fits remains unaddressed.

Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/r/20240420023543.3300306-4-kuba@kernel.org


Signed-off-by: Jakub Kicinski <kuba@kernel.org>