Move libsigchain version scripts to app_process, where they are used.

This is a temporary measure to avoid exporting filegroups in the SDK
snapshots. The version scripts will go away when libsigchain can be a
shared lib.

Test: Build and boot
Bug: 153338107
Bug: 142944043
Change-Id: Id7bff041413569342cc5dcaeff144287b2ae1ef9