selftests/bpf: Use start_server_str in do_test in bpf_tcp_ca

selftests/bpf: Use start_server_str in do_test in bpf_tcp_ca

This patch uses new helper start_server_str() in do_test() in bpf_tcp_ca.c
to accept a struct network_helper_opts argument instead of using
start_server() and settcpca(). Then change the type of the first paramenter
of do_test() into a struct network_helper_opts one.

Define its own cb_opts and opts for each test, set its own cc name into
cb_opts.cc, and cc_cb() into post_socket_cb callback, then pass it to
do_test().

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Link: https://lore.kernel.org/r/6e1b6555e3284e77c8aa60668c61a66c5f99aa37.1716638248.git.tanggeliang@kylinos.cn
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>