Add basic support of BPF token to BPF_PROG_LOAD. BPF_F_TOKEN_FD flag
should be set in prog_flags field when providing prog_token_fd.

Wire through a set of allowed BPF program types and attach types,
derived from BPF FS at BPF token creation time. Then make sure we
perform bpf_token_capable() checks everywhere where it's relevant.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20240124022127.2379740-7-andrii@kernel.org