bpf,selinux: allocate bpf_security_struct per BPF token

Utilize newly added bpf_token_create/bpf_token_free LSM hooks to
allocate struct bpf_security_struct for each BPF token object in
SELinux. This just follows similar pattern for BPF prog and map.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20231130185229.2688956-18-andrii@kernel.org


Signed-off-by: Alexei Starovoitov <ast@kernel.org>