Support using spark application metrics as operator metrics labels

[amit-mazor]

Goal:

This PR's goal is to allow adding additional labels to the operator metrics.

Currently, the only available label in the operator metrics is app_type, but I think it is very useful to add additional labels from our spark applications.

For example internally, I added two labels in addition to 'app_type' that Im using in order to create alerts.

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[amit-mazor]

@liyinan926 Can you please review ?