[analyzer] Move convenience REGISTER_*_WITH_PROGRAMSTATE to CheckerContext.h

As Anna pointed out, ProgramStateTrait.h is a relatively obscure header,
and checker writers may not know to look there to add their own custom
state.

The base macro that specializes the template remains in ProgramStateTrait.h
(REGISTER_TRAIT_WITH_PROGRAMSTATE), which allows the analyzer core to keep
using it.

llvm-svn: 167385