Merge pull request #29124 from SheliaJimenez:dnn-pow-fix

Dnn pow layer output type fix #29124

### Description

This pull request needs https://github.com/opencv/opencv_extra/pull/1372 to run.

**issue:** when running disk-lightglue `.onnx` model, such error message is thrown:

```bash
Error message OpenCV(5.0.0-pre) /home/tapakya/cpp/opencv_mod/opencv/modules/dnn/src/layers/nary_eltwise_layers.cpp:410: error: (-2:Unspecified error) in function 'virtual void cv::dnn::NaryEltwiseLayerImpl::getTypes(const std::vector<int>&, int, int, std::vector<int>&, std::vector<int>&) const'
> All inputs should have equal types (expected: 'inputs[0] == input'), where
>     'inputs[0]' is 11 (CV_64SC1)
> must be equal to
>     'input' is 5 (CV_32FC1)
```

This is because in `nary_eltwise_layers.cpp`, `getTypes` didn't set the output type of power operation correctly. `int`^`float` should output `float`, whereas `getTypes` set the output type to `int` in this case.

```c++
        if (op == OPERATION::POW) {
            CV_Assert(inputs.size() == 2);
            auto isIntegerType = [](int t) {
                return t == CV_8S || t == CV_8U || t == CV_16S || t == CV_16U || t == CV_32S || t == CV_32U || t == CV_64S || t == CV_64U;
            };
            auto isFloatType = [](int t) {
                return t == CV_32F || t == CV_64F || t == CV_16F || t == CV_16BF;
            };

            int out_type;
            const bool baseIsInt   = isIntegerType(inputs[0]);
            const bool expIsInt    = isIntegerType(inputs[1]);
            const bool baseIsFloat = isFloatType(inputs[0]);
            const bool expIsFloat  = isFloatType(inputs[1]);

            if ((baseIsInt && expIsInt) || (baseIsFloat && expIsFloat))
            {
                out_type = (inputs[0] == inputs[1]) ? inputs[0] : CV_32F;
            }
            else if (baseIsFloat != expIsFloat)
            {
                out_type = inputs[0];
                // if base is int and exp is float, output type should be float
            }
```

**fix:** corrected the logic of determining output type

```c++
            if ((baseIsInt && expIsInt) || (baseIsFloat && expIsFloat))
            {
                out_type = (inputs[0] == inputs[1]) ? inputs[0] : CV_32F;
            }
            else if (baseIsFloat && !expIsFloat)
            {
                out_type = inputs[0];
            }
            else if (!baseIsFloat && expIsFloat)
            {
                out_type = CV_32F;
            }
```

### Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [ ] There is a reference to the original bug report and related work
- [x] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [ ] The feature is well documented and sample code can be built with the project CMake

modules/dnn/src/layers/nary_eltwise_layers.cpp

@@ -406,10 +406,14 @@ public:
             {
                 out_type = (inputs[0] == inputs[1]) ? inputs[0] : CV_32F;
             }
-            else if (baseIsFloat != expIsFloat)
+            else if (baseIsFloat && !expIsFloat)
             {
                 out_type = inputs[0];
             }
+            else if (!baseIsFloat && expIsFloat)
+            {
+                out_type = CV_32F;
+            }
             else
             {
                 out_type = CV_32F;