[llvm][STLExtras] Move various iterator/range utilities from MLIR to LLVM
This revision moves the various range utilities present in MLIR to LLVM to enable greater reuse. This revision moves the following utilities:
This is set of utility iterator/range base classes that allow for building a range class where the iterators are represented by an object+index pair.
Given a range of pairs, returns a range iterating over the second elements.
Returns if the given range has 1 element. size() == 1 checks end up being very common, but size() is not always O(1) (e.g., ilist). This method provides O(1) checks for those cases.
Differential Revision: https://reviews.llvm.org/D78064