Replace mhlo ops with core dialect ops in more tests. (#9838)

Progress on https://github.com/iree-org/iree/issues/9667, working towards removing MHLO and other input dialects from the "core" parts of the IREE compiler. Any tests using input dialects should be organized under the relevant `compiler/InputConversion/*` or `tests/e2e/*_ops/` directories.

Notable remaining tests using mhlo in the "core" of the compiler:
* [demote_f32_to_f16.mlir](https://github.com/iree-org/iree/blob/main/compiler/src/iree/compiler/Dialect/Util/Transforms/test/demote_f32_to_f16.mlir)
* [demote_f64_to_f32.mlir](https://github.com/iree-org/iree/blob/main/compiler/src/iree/compiler/Dialect/Util/Transforms/test/demote_f64_to_f32.mlir)
* [demote_i64_to_i32.mlir](https://github.com/iree-org/iree/blob/main/compiler/src/iree/compiler/Dialect/Util/Transforms/test/demote_i64_to_i32.mlir)
* [promote_f16_to_f32.mlir](https://github.com/iree-org/iree/blob/main/compiler/src/iree/compiler/Dialect/Util/Transforms/test/promote_f16_to_f32.mlir)
diff --git a/samples/static_library/simple_mul.mlir b/samples/static_library/simple_mul.mlir
index e5f4d5b..0b8a2f0 100644
--- a/samples/static_library/simple_mul.mlir
+++ b/samples/static_library/simple_mul.mlir
@@ -1,5 +1,4 @@
-func.func @simple_mul(%arg0: tensor<4xf32>, %arg1: tensor<4xf32>) -> tensor<4xf32>
-{
-  %0 = "arith.mulf"(%arg0, %arg1) {name = "mul.1"} : (tensor<4xf32>, tensor<4xf32>) -> tensor<4xf32>
+func.func @simple_mul(%arg0: tensor<4xf32>, %arg1: tensor<4xf32>) -> tensor<4xf32> {
+  %0 = "arith.mulf"(%arg0, %arg1) : (tensor<4xf32>, tensor<4xf32>) -> tensor<4xf32>
   return %0 : tensor<4xf32>
 }