[DebugInfo][InstrRef] Ignore SP clobbers on call instructions even more

Avoid un-necessarily recreating DBG_VALUEs on call instructions.

In LiveDebugvalues we choose to ignore any clobbers of SP by call
instructions, as they're irrelevant to our model of the machine. We
currently do so for tracking register values (MTracker); do the same for
tracking variable locations (TTracker).

Test modified to endure that a duplicate DBG_VALUE is not created after the
call in struction in this test.

Differential Revision: https://reviews.llvm.org/D114365