This commit contains several code changes which are ultimately required for converting the varions Merger identifiers from typedefs to newtypes. The actual implementation of the newtypes themselves has been split off into separate commits, in hopes of simplifying the review process.
Depends On D146561
Can you leave this in the same place for now (and not introduce a new MergerNewtypes.h). I am not convinced yes we really need two headers in the end, and even if so, we can have an intermediate revision that just moves this out. That way, I can focus on the real changes in the CL.