Generate monolithic hidden API files direct from class jars

Previously, the monolithic hidden API files, e.g. hiddenapi-index.csv
file, were generated in two steps. First, each module created its own
files using the information in its class jars. Then, the monolithic
files were created by merging those module specific files into a larger
file.

This change switches to generating the monolithic files directly from
the class jar files and bypassing the intermediate files.

In order to ensure that this change did not change the monolithic files
it is necessary for the hiddenapi-metadata.csv to go through a
reformatting step. Hopefully, this will be able to be removed in a
follow up change.

Bug: 179354495
Test: verified that the monolithic out/soong/hiddenapi/... files are
      unchanged by this change
Change-Id: I5a78e747516014b7c0f402a4b4431b14be6a84b2