getnameinfo: Copy lwip adapter code from `lib/newlib`

getnameinfo: Copy lwip adapter code from `lib/newlib`

This commit copies the lwip glue code for `getnameinfo()` from `lib/newlib`
(https://github.com/unikraft/lib-newlib/commit/727d5eabd48f329df179be4a37dd40dd5d71151b,
 Commit 727d5ea) to musl. It is only enabled if musl is configured to
forward DNS related requests to lwIP.

Signed-off-by: Simon Kuenzer <simon@unikraft.io>
Reviewed-by: Stefan Jumarea <stefanjumarea02@gmail.com>
Reviewed-by: Mihnea Firoiu <mihneafiroiu0@gmail.com>
Reviewed-by: Razvan Deaconescu <razvand@unikraft.io>
Approved-by: Razvan Deaconescu <razvand@unikraft.io>
GitHub-Closes: #74