Add framework boot image

Currently, it is just a placeholder that retrieves information about
the framework boot image from the dex_bootjars singleton.

Bug: 177892522
Test: m droid
Change-Id: Icd7943a37378a56c416e502aa29d6088c2f247d2
Exempt-From-Owner-Approval: https://crbug.com/gerrit/14008