selftests/bpf: Add strparser test for bpf

Add test cases for bpf + strparser and separated them from
sockmap_basic, as strparser has more encapsulation and parsing
capabilities compared to standard sockmap.

Signed-off-by: Jiayuan Chen <mrpre@163.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Acked-by: Jakub Sitnicki <jakub@cloudflare.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://patch.msgid.link/20250122100917.49845-6-mrpre@163.com