[NFC][DivRemPairs] Tests with rem in expanded form (PR42673)

As discussed in https://bugs.llvm.org/show_bug.cgi?id=42673
there is a TTI hook hasDivRemOp() that matters here.
While -div-rem-pairs will decompose 'rem' if that hook returns false,
nothing does the opposite transform.

We can't to this in InstCombine, because it does not currently
access TTI, and i'm not sure we should change that.

We can't really do that in DAGCombine since it also currently does not
access TTI.

Therefore only DivRemPairs is left.

https://bugs.llvm.org/show_bug.cgi?id=42673

llvm-svn: 367046