[Fix] add Config hyperparameters for clearml backend

[gntoni]

Motivation

This PR allows to have better logging of hyperparameters when using ClearML backend.

Modification

Currently, the clearml viz backend add_cfg() function calls Task.connect_configuration()).
As stated in the clearml documentation this will save the cfg file as a blog. This is useful for logging purposes but not much use beyond that.

By saving it with Task.set_parameters_as_dict() instead, clearml will be aware of the internal structure of the config dictionary and the hyperparameters in it can be used for visualization and evaluation (i.e. we can compare experiments with respect to their hyperparameters)

Checklist

1. Pre-commit or other linting tools are used to fix the potential lint issues.
2. The modification is covered by complete unit tests. If not, please add more unit test to ensure the correctness.
3. If the modification has potential influence on downstream projects, this PR should be tested with downstream projects, like MMDetection or MMPretrain.
4. The documentation has been modified accordingly, like docstring or example tutorials.

[CLAassistant]

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