AIP-84 | Add multisort to dags list request

In the UI, we default the dags list to show dags with the latest dag run first , which we pass as `-last_dag_run_start_date`. Problem is that the minus symbol seems to make the default sorts also reverse so any dags without a dag run will be in reverse alphabetical order which is counterintuitive for users.
If you reverse the dag run start date order, it will also change the alphabetical order.

Start by tracing the UI's dags list request and the `-last_dag_run_start_date` sort parameter. Confirm how multisort is represented and tested; done means dag run dates remain descending while dags without a run retain intuitive alphabetical ordering.

Written by the indexing model from the issue text.