Switch from version script to APEX stubs for libdexfile_external and add it

to the Runtime APEX.

Test: m checkbuild dist
Test: m
Test: m oatdumps
Test: Flash and boot
Test: art/build/apex/runtests.sh
Bug: 119632407
Bug: 120670568
Bug: 122885634
Change-Id: Ib98a8f7dbb1e94f553a7ebe575f320dbbebad292