Remove test_com.android.os.statsd from apex_available

In order to simplify the apex logic in Soong, avoid needing to mention
test apexes in apex_available by setting apex_available_name in the
test apex to masquerade as the corresponding non-test apex.

Bug: 383592644
Test: builds
Flag: EXEMPT refactor
Change-Id: Ia7e76503ff6213cedc7230be56aef843dbe45451