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
Merged-In: I5d2c0685b74ea5ba368c777d9646b9d3ac24dca9
Change-Id: I980111b4b83d16ccd9d3a277ab2587bf638a2c8a