Refactor library path representation in dexpreopt.

This is a preliminary CL before fixing on-device paths to DEX jars.
It groups together the inormation about on-host build paths and
on-device install paths to library DEX jars.

This CL changes the structure of module dexpreopt.config files
generated by the build system. Aside of that, no functional changes.

Test: lunch aosp_cf_x86_phone-userdebug && m
Change-Id: I8e92829885f26522aa2b936e77e91ce91593b27c