Add PearsonCorrelation metric

[kzkadc]

Description: added Pearson correlation coefficient metric to ignite.contrib.metrics.regression.

Check list:

• New tests are added (if a new feature is added)
• New doc strings: description and/or example code are in RST format
• Documentation is updated (if required)

[vfdev-5]

@kzkadc thanks for the PR, I haven't yet reviewed it in details, just a remark on the code location which could be better to be at ignite.metrics. We have a on-going work on moving contrib metrics to ignite.metrics and gradually removing the content of the contrib module keeping BC.

[kzkadc]

@vfdev-5 Is it better to create ignite.metrics.regression and place this metric there?

[vfdev-5]

@kzkadc yes, we'll move all ignite.contrib.metrics into ignite.metrics very soon, so I'd say let's just update your PR such that the metric is in ignite.metrics but we are using from ignite.contrib.metrics.regression._base import _BaseRegression temporarily.

[vfdev-5]

Please also fix code formatting issue

https://github.com/pytorch/ignite/actions/runs/8469886156/job/23234585039?pr=3212

 + flake8 ignite tests examples --config setup.cfg
ignite/metrics/regression/pearson_correlation.py:12:121: E501 line too long (122 > 120 characters)
ignite/metrics/regression/pearson_correlation.py:15:121: E501 line too long (142 > 120 characters)
Error: Process completed with exit code 1.

[vfdev-5]

Thanks a lot for working on this PR, @kzkadc !

Let's see if CI is globally passing the tests and it would be good to land it

[vfdev-5]

@kzkadc can you please fix the issue with the implementation using non-cpu device:

self = <ignite.metrics.regression.pearson_correlation.PearsonCorrelation object at 0x7f2525d75150>
output = (tensor([0.9835, 0.2422, 0.7872, 0.0981, 0.6317, 0.2422, 0.2035, 0.0723, 0.5486,
        0.7612, 0.1874, 0.8356, 0.584...409e-03, 5.2258e-02, 7.6632e-01, 4.5562e-02,
        5.4043e-01, 4.6115e-01, 3.9585e-01, 5.3294e-01], device='cuda:0'))

    def _update(self, output: Tuple[torch.Tensor, torch.Tensor]) -> None:
        y_pred, y = output[0].detach(), output[1].detach()
>       self._sum_of_y_preds += y_pred.sum()
E       RuntimeError: Expected all tensors to be on the same device, but found at least two devices, cuda:0 and cpu!

https://github.com/pytorch/ignite/actions/runs/8490646759/job/23261938233#step:9:904