[utils] InlineFunction: fix for debug info affecting optimizations

Summary:
Debug info affects output from "opt -inline", InlineFunction could
not handle the llvm.dbg.value when it exist between alloca
instructions.

Problem was that the first alloca in a sequence of allocas was
handled differently from the subsequence alloca instructions. Now
all static alloca instructions are treated the same (being removed
if the have no uses). So it does not matter if there are dbg
instructions (or any other instructions) in between.

Fix the issue: https://bugs.llvm.org/show_bug.cgi?id=43291k

Patch by: yechunliang (Chris Ye)

Reviewers: bjope, jmorse, vsk, probinson, jdoerfert, mtrofin, aprantl, fhahn

Reviewed By: bjope

Subscribers: uabelho, ormris, aprantl, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D68633