CodeGen: Create a proper ModuleSlotTracker for MachineInstr
CodeGen: Create a proper ModuleSlotTracker for MachineInstr

Another follow-up related to r240848: try a little harder to share slot
tracking calculations within a single `MachineInstr` dump.  This is
unrelated to `MachineFunction::print()`, since that should be passing
through the function's `ModuleSlotTracker` by now, but could affect the
speed of dumping from a debugger if there is more than one IR-level
operand.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@240852 91177308-0d34-0410-b5e6-96231b3b80d8

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