Add test to target_lib.py.

Add test to two classes: BuildInfo and TargetLib. BuildInfo is a
dataclass which can store and parse Android Build informations from an
OTA package. TargetLib is a database interface which can be used to
store and extract BuildInfo.

Please refer to this CL for more details of these two classes:
https://android-review.googlesource.com/c/platform/development/+/1735315

Test: python test_target_lib.py -v
Change-Id: I3b2143af7f3708207b6c53744d903d3dcee92d55
5 files changed