Improve View docs

[t92549]

The filtering documentation mentions using a View and briefly describes what a View can do. However, it should have a detailed section which describes what things can go inside a view element definition and the order in which they apply.

With the main steps being:

• preAggregationFilterFunctions
• groupBy
• aggregator
• postAggregationFilterFunctions
• transformFunctions
• postTransformFilterFunctions

Specifically, it would be good to provide examples to show how order is important and can change the results depending on groupBy and whether filtering is pre or post aggregation.