Display readable labels for all options in parameter dropdown.

## Description

When you create "Dropdown" -> "Values of field" parameter the suggested field values are not always readable:

- nodes, inputs and streams display the entity id like "000000000000001" instead of "Default Stream"
For aggregation this has been improved with https://github.com/Graylog2/graylog2-server/pull/15464

- booleans will be displayed as "1" or "0" instead of "true" or "false". This already works for field value suggestions in the query input.

- timestamps will be displayed as unix time stamp instead of a readable format.