Rename `libnetworkstacktestsjni` to `libapfjni` for clarity

To prevent misunderstanding between `libnetworkstackjni` and `libnetworkstacktestsjni`, rename it to `libapfjni` for clarity.

Bug: 391118179
Test: atest NetworkStackTests
Change-Id: Ie384f5e83e1d9ec015f5fa5965a76468751ae955
4 files changed