Merge branch 'libbpf: Deprecate bpf_{map,program}__{prev,next} APIs since v0.7'

Hengqi Chen says:

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bpf_{map,program}__{prev,next} don't follow the libbpf API naming
convention. Deprecate them and replace them with a new set of APIs
named bpf_object__{prev,next}_{program,map}.

v1->v2: [0]
  * Addressed Andrii's comments

  [0]: https://patchwork.kernel.org/project/netdevbpf/patch/20210906165456.325999-1-hengqi.chen@gmail.com/


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