The op used to support only float element types. This was inconsistent
with `ConstantOp::isBuildableWith`, which allows integer element types.
The complex type allows any float/integer element type.
Note: The other complex dialect ops do not support non-float element
types yet. The main purpose of this change to fix
`Tensor/canonicalize.mlir`, which is currently failing when verifying
the IR after each pattern application (#74270).
```
within split at mlir/test/Dialect/Tensor/canonicalize.mlir:231 offset :8:15: error: 'complex.constant' op result #0 must be complex type with floating-point elements, but got 'complex<i32>'
%complex1 = tensor.extract %c1[] : tensor<complex<i32>>
^
within split at mlir/test/Dialect/Tensor/canonicalize.mlir:231 offset :8:15: note: see current operation: %0 = "complex.constant"() <{value = [1 : i32, 2 : i32]}> : () -> complex<i32>
"func.func"() <{function_type = () -> tensor<3xcomplex<i32>>, sym_name = "extract_from_elements_complex_i"}> ({
%0 = "complex.constant"() <{value = [1 : i32, 2 : i32]}> : () -> complex<i32>
%1 = "arith.constant"() <{value = dense<(3,2)> : tensor<complex<i32>>}> : () -> tensor<complex<i32>>
%2 = "arith.constant"() <{value = dense<(1,2)> : tensor<complex<i32>>}> : () -> tensor<complex<i32>>
%3 = "tensor.extract"(%1) : (tensor<complex<i32>>) -> complex<i32>
%4 = "tensor.from_elements"(%0, %3, %0) : (complex<i32>, complex<i32>, complex<i32>) -> tensor<3xcomplex<i32>>
"func.return"(%4) : (tensor<3xcomplex<i32>>) -> ()
}) : () -> ()
```
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