Add a system variant of the merged annotations

This is going to be disted instead of the monolithic one being
used currently.

Bug: 235140934
Test: m sdk-annotations{,-system}.zip and diff; manual spot checking
Test: m sdk dist && diff out/dist/system-data/annotations.zip with this
Change-Id: I9874f88e933a8b804a73638e6bac7a9d312c7c9f