Give AppZygote process shared app GID.

So AppZygote can access profiles belonging to the app.

Bug: 254422654
Flag: EXEMPT bugfix
Test: inspect /proc/pid/maps to verify profiles are loaded
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:60c4ffb1dcce3a76de9d58ca9f8b6e3bc3e3dd94)
Merged-In: Ibf0f43accff687bfe172796086124f77eeca574d
Change-Id: Ibf0f43accff687bfe172796086124f77eeca574d