selftests/bpf: Optionally select broadcasting flags

selftests/bpf: Optionally select broadcasting flags

Broadcasting flags are hardcoded for each kind for protocol.

Create a redirect_flags map that allows to select the broadcasting flags
to use in the bpf_redirect_map(). The protocol ID is used as a key.
Set the old hardcoded values as default if the map isn't filled by the
BPF caller.

Signed-off-by: Bastien Curutchet (eBPF Foundation) <bastien.curutchet@bootlin.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20250212-redirect-multi-v5-3-fd0d39fca6e6@bootlin.com