Make safeunion@1.0 test HAL Java-compatible

This change removes Java-incompatible types (memory, handle) from the
safeunion@1.0 test HAL. Moving forward, the idea is to keep this HAL
Java & C++-friendly, and create another version (likely safeunion@2.0)
to regress on C++-only types; tracked by b/110269925.

Bug: n/a
Test: Ran the existing hidl_test suite
Change-Id: Ic7458c3f5b571e77e5f894a9854a2b201f53fe18