[mlir] Use arith max or min ops instead of cmp + select (#82178)

I believe the semantics should be the same, but this saves 1 op and simplifies the code.

For example, the following two instructions:

```
%2 = cmp sgt %0, %1
%3 = select %2, %0, %1
```

Are equivalent to:

```
%2 = maxsi %0 %1
```