hs: Refactoring of some part of the legacy code for prop224 usage
This branch contains 4 commits that we need for prop224 service implementation work (legacy/trac#20657 (moved)).
First commit is a trivial refactor to make a function in rendservice.c public and broader to both HS subsystems (legacy and new).
Second and third commit are code moving and minor cleanup.
Fourth commit is a bit more involving that is making the pruning rendservice list public so the HS prop224 code can use it later on with legacy/trac#20657 (moved) work.