Fix RadioMetadata.hashCode().

ag/7063548 implemented RadioMetadata.hashCode() by calling Bundle.hashCode(),
but that function uses the default implementation that uses the address
of the Bundle. As a result, two RadioMetadata objects that were equal
probably had different hash codes.

RadioMetadata now instead lazily computes its hash code based upon the keys and
values in mBundle.

Fixes: 130750904
Test: atest com.android.server.broadcastradio.hal2.StartProgramListUpdatesFanoutTest
Change-Id: Ia49716594744871831bc3734aea37e0f505897bf