Implement libbpf bpf_program API

We should expose all of the bpf_program api, just being careful about what is deprecated and/or discouraged when 1.0 is released.

- [ ] bpf_program__set_ifindex
- [ ] bpf_program__name
- [ ] bpf_program__section_name
- [ ] bpf_program__autoload
- [x] bpf_program__set_autoload
- [x] bpf_program__fd
- [x] bpf_program__pin
- [x] bpf_program__unpin
- [ ] bpf_program__unload
- [x] bpf_program__attach
- [x] bpf_program__attach_perf_event
- [ ] bpf_program__attach_perf_event_opts
- [x] bpf_program__attach_kprobe
- [ ] bpf_program__attach_kprobe_opts
- [x] bpf_program__attach_uprobe
- [ ] bpf_program__attach_uprobe_opts
- [x] bpf_program__attach_tracepoint
- [ ] bpf_program__attach_tracepoint_opts
- [x] bpf_program__attach_raw_tracepoint
- [ ] bpf_program__attach_trace
- [ ] bpf_program__attach_trace_opts
- [x] bpf_program__attach_lsm
- [x] bpf_program__attach_cgroup
- [x] bpf_program__attach_netns
- [x] bpf_program__attach_xdp
- [ ] bpf_program__attach_freplace
- [x] bpf_program__attach_iter
- [x] bpf_program__type
- [x] bpf_program__set_type
- [ ] bpf_program__expected_attach_type
- [x] bpf_program__set_expected_attach_type
- [x] bpf_program__set_attach_target

Low-level API:

- [ ] bpf_prog_get_info_by_fd

Start by reading the existing bpf_program bindings and comparing the unchecked entries in the API checklist with the corresponding libbpf API, including bpf_prog_get_info_by_fd. Determine which deprecated or discouraged functions should be exposed before 1.0; done means the supported remaining APIs are available with the existing bindings’ conventions.

Written by the indexing model from the issue text.