Change permitted_packages check to be per-jar rather than per-apex

(This CL has been implemented in master to prevent a merge conflict with
ag/16222633. It will be cherry-picked to AOSP)

Summary:
- updates the Q and R maps, the new keys are the bcp jars and not the
apexes. neverallow build rules ensure that these bcp jars have a
restricted set of permitted_packages
- remove BootclasspathJar from the neverallow rule. This is no longer
necessary since the keys in the maps are the bootjars themselves, and
not apexes

Bug: 205289292
Test: In build/soong, go test ./apex
Change-Id: Icb91de934181a8b6f085e03a0ce8c5e08504ff94