[FEATURE] Add ability to choose multiple indices/aliases/index pattern in detector creation

[amitgalitz]

Is your feature request related to a problem?
Currently although AD backend supports multiple indices, our frontend doesn't support this, we only allow selection of one data source and for the any of the other fields that look at the index mapping we default to only look at one index.

What solution would you like?

• We should allow multiple data source selection and we should display the fields from all indices when users are selecting their data filters, timestamp, feature fields, and categorical fields.
• On both the configuration details and review and create page there should be an intuitive view of the chosen indices and their originating clusters
• During creation we should also not reset feature selection if more indices are added, we currently reset entire model configurations if an index has changed. This should only be done if an index has been removed from the list of indices selected.