[InstSimplify] add folds for and-of-icmps with same operands

All of these (and a few more) are already handled by InstCombine,
but we shouldn't have to wait until then to simplify these because
they're cheap to deal with here in InstSimplify.

This is the 'and' sibling of the earlier 'or' patch:
https://reviews.llvm.org/rL288833

llvm-svn: 288841