[SROA] Start more deeply moving SROA to use ranges rather than just
iterators.
There are a ton of places where it essentially wants ranges
rather than just iterators. This is just the first step that adds the
core slice range typedefs and uses them in a couple of places. I still
have to explicitly construct them because they've not been punched
throughout the entire set of code. More range-based cleanups incoming.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219955
91177308-0d34-0410-b5e6-
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