Allow platform to recognize compressed APEX

Because compressed APEX files have a different file extension (.capex)
than normal APEX (.apex), they are ignored by apexd.

This CL allows apexd to find compressed APEX files using .capex
extension and treat it like an "inactive factory APEX".

Bug: 172911820
Test: atest apex_compression_platform_tests
Test: atest ApexFileTest
Test: atest ApexPreinstalledDataTest
Change-Id: I188ecbf1a0c6726941d8b26895039040586b3f9a
15 files changed