[StackColoring] Remap FixedStackPseudoSourceValue frame index referenced by MachineMemOperand

StackColoring::remapInstructions() remaps MachineOperand frame index (e.g. %stack.1 -> %stack.0)
but does not remap FixedStackPseudoSourceValue frame index (e.g. store 4 into %stack.1.ap2.i.i)
referenced by MachineMemoryOperand.

This can cause an assertion failure when LiveDebugValues references a dead stack object.

It is difficult to craft a test case. -g, va_copy and stack-coloring are required.
I can only reproduce it on ppc32.