Prepare for removal of legacy-test from default targets

In preparation for removing junit classes from the Android API
the legacy-test target will be removed from the
TARGET_DEFAULT_JAVA_LIBRARIES. This change adds explicit
dependencies on junit and/or legacy-android-test to ensure that
modules will compile properly once it is removed.

Bug: 30188076
Test: make checkbuild
Change-Id: I3ac2ec9b145df5872045a44cc9a7aeb24c456c80