[mlir][gpu] Align reduction operations with vector combining kinds (#73423)

The motivation for this change is explained in
https://github.com/llvm/llvm-project/issues/72354.

Before this change, we could not tell between signed/unsigned
minimum/maximum and NaN treatment for floating point values.

The mapping of old reduction operations to the new ones is as follows:
*  `min` --> `minsi` for ints, `minf` for floats
*  `max` --> `maxsi` for ints, `maxf` for floats

New reduction kinds not represented in the old enum: `minui`, `maxui`,
`minimumf`, `maximumf`.

As a next step, I would like to have a common definition of combining
kinds used by the `vector` and `gpu` dialects. Separately, the GPU to
SPIR-V lowering does not yet properly handle zero and NaN values -- the
behavior of floating point min/max group reductions is not specified by
the SPIR-V spec, see https://github.com/llvm/llvm-project/issues/73459. 

Issue: https://github.com/llvm/llvm-project/issues/72354