Remove implementation details from media hidden api flags

Ran the following to compute the set of split_packages and
package_prefixes properties.
    m analyze_bcpf &&
    analyze_bcpf --bcpf com.android.media-bootclasspath-fragment

Bug: 194063708
Test: m out/soong/hiddenapi/hiddenapi-flags.csv
Change-Id: I53e07203cda00351e64ee0917ae7150e20f4f2a0