[AssumeBundles] Remove non-determinisme from assume builder

Summary:
The assume builder was non-deterministic when working on unamed values.
this patch fixes this.

Reviewers: jdoerfert

Reviewed By: jdoerfert

Subscribers: hiraditya, mgrang, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D78616