Move the bootclasspath_fragment to be part of an apex to match how they
are expected to be used. Also adds the bar library to the boot jars
config as every module in a bootclasspath_fragment that is referenced
from a platform_bootclasspath module is expected to be in the config.
Bug: 179354495
Test: m nothing
Merged-In: I6f826dce9c006d630ee31d4171fe6fb458cc9442
Change-Id: I6f826dce9c006d630ee31d4171fe6fb458cc9442
(cherry picked from commit dc3f9566a2ab5f23f2e9f0fd7e22820d4e3c53b5)