Making Instrumentation aware of LoopNest Pass

Intrumentation callbacks are not made aware of LoopNest passes. From the loop pass manager, we can pass the outermost loop of the LoopNest to instrumentation in case of LoopNest passes.

The current patch made the change in two places in StandardInstrumentation.cpp. I will submit a proper patch where the OuterMostLoop is passed from the LoopPassManager to the call backs. That way we will avoid making changes at multiple places in StandardInstrumentation.cpp.

A testcase also will be submitted.

Reviewed By: aeubanks

Differential Revision: https://reviews.llvm.org/D102463