Add support for `classification_report`

[hekaisheng]

Is your feature request related to a problem? Please describe. Implements classification_report for classification metrics.(https://scikit-learn.org/stable/modules/generated/sklearn.metrics.classification_report.html)

[GaneshSingh757]

Hi. I would like to work on this feature, can you please give me a little more detail?....Do we need to add a new script inside "mars/mars/metrics/" that generates the classification report?

[tsabbir96]

@hekaisheng Hi, Can I continue to this issue if that's okay?

As far as I understood the requirements are something like this:

• Implement a function that can generate reports for the major classification metrics.

My questions:

• Should I assume that this function should be kept in this directory: mars/mars/metrcs? Or should I create a backend just like prometheus or console for this ?