Calculate widest stub dex jars per module

Previously, the stub dex jars for each HiddenAPIScope was created by
merging the stub dex jars provided by each module for that scope. Then
the widest stub dex jars were chosen. So, if module A provided public,
system and test stub dex jars and module B provided only public then
the stub dex jars for each scope would be:
* public -> A,B
* system -> A
* test -> A

So, the widest API scope for which there are stub dex jars is "test"
and so the widest stub dex jars would just come from module A and not
module B. So, when "hiddenapi list" is run for module C which depends
on modules A and B it only gets given stub dex jars for module A which
means that it cannot resolve all the types that C may use which can
lead to incorrect flags being generated.

This change does not merge the stub dex jars from each module together
and instead keeps them separate by module. The widest stub dex jars
list is constructed by asking each module in turn for their widest stub
dex jars. e.g. Given the above example we would have:

Module A:
* public
* system
* test <- widest

Module B:
* public <- widest

So, the widest stub dex jars will be A's test and B's public stub dex
jars.

Bug: 179354495
Test: m out/soong/hiddenapi-flags.csv
      - make sure that this does not change the file.
Change-Id: Ib137825ebffe94b2bf220732bae6077f7b7ac6db