Support multiple properties in data queries

[hwandersman]

Is your feature request related to a problem? Please describe.
For the IoT SiteWise Get* queries (GetPropertyValue, GetPropertyValueHistory, GetInterpolatedValues, and GetPropertyAggregates) we support selecting multiple assets in the same asset model, but we do not support selecting multiple properties for those assets. Many IoT SiteWise customers are asking for this feature.

Describe the solution you'd like
Like we batch calls to the Get* APIs for multiple assets, we should have additional entries in the batch request for multiple properties.

Each entry to a batch data call must have at least an assetId and property OR a property alias. The scope for this feature is to support a list of assetIds and propertyIds and return data for all combinations of those ids. Every combination is valid as long as each asset is an instance of the same asset model.

The backend plugin will need to update models to accept an array of propertyIds like assetIds, then create entries for the respective batch API like here: https://github.com/grafana/iot-sitewise-datasource/blob/main/pkg/sitewise/api/property_history_batch.go#L48

The frontend plugin will need to update the propertyId field to support multiple values.

Describe alternatives you've considered
The only alternative is to create a new query for each property, which is not extensible for customers with many properties on their assets.

Additional context
N/A