Support pruning properties by build release

Adds a general mechanism for pruning selected sdk member properties
(i.e. setting their fields to their zero value) and uses that to prune
any properties that do not support a specified target build release.

Follow up changes will use that to allow building an sdk snapshot that
is compatible with previous release S.

Bug: 197842263
Test: m nothing
Change-Id: Ib949a9cfe85fff30f86228eeb15d3a45c073b037