bpf: Factor out socket lookup functions for the TC hookpoint.

bpf: Factor out socket lookup functions for the TC hookpoint.

[ Upstream commit 6e98730bc0b44acaf86eccc75f823128aa9c9e79 ]

Change BPF helper socket lookup functions to use TC specific variants:
bpf_tc_sk_lookup_tcp() / bpf_tc_sk_lookup_udp() / bpf_tc_skc_lookup_tcp()
instead of sharing implementation with the cg / sk_skb hooking points.
This allows introducing a separate logic for the TC flow.

The tc functions are identical to the original code.

Signed-off-by: Gilad Sever <gilad9366@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Shmulik Ladkani <shmulik.ladkani@gmail.com>
Reviewed-by: Eyal Birger <eyal.birger@gmail.com>
Acked-by: Stanislav Fomichev <sdf@google.com>
Link: https://lore.kernel.org/bpf/20230621104211.301902-2-gilad9366@gmail.com
Stable-dep-of: 9a5cb79762e0 ("bpf: Fix bpf socket lookup from tc/xdp to respect socket VRF bindings")
Signed-off-by: Sasha Levin <sashal@kernel.org>