libbpf: clean up perfbuf APIs

Remove deprecated perfbuf APIs and clean up opts structs.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20220627211527.2245459-7-andrii@kernel.org


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