[AssumeBundles] Move to IR so it can be used by Analysis

Summary:
Assume bundles need to be usable by Analysis and Transforms/Utils isn't.
so this commit moves utilities to deal with asusme bundles to IR.

Reviewers: jdoerfert

Reviewed By: jdoerfert

Subscribers: mgorny, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D75618