[AggressiveInstCombine] Avoid load merge/widen if stores are present b/w loads

This patch is to address the test cases in which the load has to be inserted at a right point. This happens when there is a store b/w the loads.

This patch reverts the loads merge in all cases when stores are present b/w loads and will eventually be replaced with proper fix and test cases.

Differential Revision: https://reviews.llvm.org/D137333