Add libkver.

libkver is the library to parse KMI versions and kernel releases for
GKI. GKI kernel releases takes the following format:

  5.4.42-android12-0

and GKI kernel module interface versions takes the following format:

  5.4-android12-0

Also add unit test.

Test: libkver_test
Bug: 159842160
Bug: 162554855
Change-Id: Id90f4e315b1218c2980576177922bac9d67c7ad4
8 files changed