MIR Printer: Use a module slot tracker to print global address operands. NFC.

This commit adopts the 'ModuleSlotTracker' class, which was surfaced in r240842,
to print the global address operands. This change ensures that the slot tracker
won't have to be recreated every time a global address operand is printed,
making the MIR printing more efficient.

llvm-svn: 241645