[CIR] Lower constant NTTP objects (#194496)
Like my previous patch, this just stores an NTTP object as a global
(using the same code, with 1 level of indrection slipped off), and
initializes it as a const. This patch also fleshes out the
CIRGenExprConstant.cpp area, leaving just 2 'NYI's in the area, 1 of
which is the MSGuidAttr again.
