[MemProf] Fix callee guid for non-leaf frame (#172502)
When matching callsite profile info, we synthesize VP metadata for
matched indirect calls from the CalleeGuids recorded with the CallSite
profile info. However, those are the callee guids of the leaf-most frame
in the callsite. In cases where we match to a portion of the frames, not
including the leaf, the callee guid should instead be synthesized from
the next leaf-most frame in the list.
This addresses the case where indirect call promotion was applied in the
profiled binary during SamplePGO matching in a ThinLTO backend, where we
didn't have VP metadata.
