Merge branch 'libbpf 1.0: deprecate bpf_map__def() API'

Christy Lee says:

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

bpf_map__def() is rarely used and non-extensible. bpf_map_def fields
can be accessed with appropriate map getters and setters instead.
Deprecate bpf_map__def() API and replace use cases with getters and
setters.

Changelog:
----------
v1 -> v2:
https://lore.kernel.org/all/20220105230057.853163-1-christylee@fb.com/

* Fixed commit messages to match commit titles
* Fixed indentation
* Removed bpf_map__def() usage that was missed in v1
====================

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