The original reimplementation of EDSC as declarative builders and the
subsequent rework of Python bindings forbade to use the (true) division
operator for values of the index types without providing an alternative. Index
types only support floor and ceil division through affine maps. Expose this to
Python bindings through a `__floordiv__` function on `ValueHandle`s.
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PiperOrigin-RevId: 241713093