[llvm-profgen] Do not cache the frame location stack during computing inlined context size

In `computeInlinedContextSizeForRange`, the offset of range is only used one time, there is no need to cache the frame location stack.
Measured on one internal service binary, this can save 2GB memory usage and reduce a small run time (avoid one hash search).

Reviewed By: hoy, wenlei

Differential Revision: https://reviews.llvm.org/D128859