Allow using updatable boot jars in dexpreopt (but don't use them yet).

This CL handles updatable boot jars in the same hacky way as we handle
non-updatable boot jars: it creates a set of predefined paths to the dex
jars in a global config, then traverses all modules in a singleton
context, finds updatable boot jars and adds copy rules from these jars
to the predefined paths. A proper way would be to register dependencies
of the dexpreopted modules on the boot jars and extracting paths to dex
files by walking these dependencies.

Bug: 178467404
Test: lunch aosp_cf_x86_64_phone-userdebug && m
Test: added new Soong test
Change-Id: I87f764109315f79315d73bf43799b70eb010fc0b