Move statsd related hidden API flag file entries to packages/modules/Statsd

Bug: 179354495
Test: m com.android.os.statsd
      - ensure that the generated APEX is byte-for-byte identical
        before and after these changes.
      m out/soong/hiddenapi/hiddenapi-flags.csv
      - make sure that they are not changed by this.
Change-Id: Iaa3d98ced5f3b67f891e5d648a5004acdf7a075c