Merge branch 'libbpf: Add btf__type_cnt() and btf__raw_data() APIs'

Hengqi Chen says:

====================

Add btf__type_cnt() and btf__raw_data() APIs and deprecate
btf__get_nr_type() and btf__get_raw_data() since the old APIs
don't follow libbpf naming convention. Also update tools/selftests
to use these new APIs. This is part of effort towards libbpf v1.0

v1->v2:
 - Update commit message, deprecate the old APIs in libbpf v0.7 (Andrii)
 - Separate changes in tools/ to individual patches (Andrii)
====================

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>