Initial import of libmnl

Third-Party Import of: https://git.netfilter.org/libmnl
Request Document: go/android3p
For CL Reviewers: go/android3p#reviewing-a-cl
For Build Team: go/ab-third-party-imports
Bug: http://b/457275163
Original import of the code can be found at: https://googleplex-android.googlesource.com/platform/external/libmnl/+/refs/heads/third-party-review
Security Questionnaire: http://b/457275163#comment1
Test: built locally

Change-Id: I9be6d326962c28c1f9b1848ac09e728d9a293bcb