Separate monolithic hidden API processing from hiddenAPIFlagFileInfo

The hiddenAPIFlagFileInfo was being used for both the input and output
of bootclasspath_fragment and platform_bootclasspath and also to pass
information around to various hidden API rule methods. Supporting
multiple different uses in this way made it hard to reason about.

This change creates a separate structure for use by the
platform_bootclasspath. Follow up changes will split out other
functionality into separate types.

Bug: 179354495
Test: m com.android.art com.android.ipsec com.android.os.statsd com.android.conscrypt
      - verify that this does not change the contents of the apex files
Change-Id: Ia5c5f65ae5645486c42819c669a8601588217f88