[globalisel][tablegen] Add support for ImmLeaf without SDNodeXForm

Summary:
This patch adds support for predicates on imm nodes but only for ImmLeaf and not for PatLeaf or PatFrag and only where the value does not need to be transformed before being rendered into the instruction.

The limitation on PatLeaf/PatFrag/SDNodeXForm is due to differences in the necessary target-supplied C++ for GlobalISel.

Depends on D36085

Reviewers: ab, t.p.northover, qcolombet, rovka, aditya_nandakumar

Reviewed By: rovka

Subscribers: kristof.beyls, javed.absar, igorb, llvm-commits

Differential Revision: https://reviews.llvm.org/D36086

llvm-svn: 311546