Allow to wait for long processes in an action workflow

This feature would allow to trigger a long process in the UI then wait for it's conclusion before continuing the pipeline. We could then refresh a data source or something like that.

We could implement the feature these ways:

• Create a poll action that polls an endpoint until some conditions are met on the result. More versatil but not the most efficient.
• Listen for a websocket that can receive events from a specific endpoint. We could add wait action that stop the workflow until it receives a notification through the endpoint. We could send the uid of the current execution (part of the context) at the url given by the wait action to say this particular execution for this particular wait action is finished. We could even have multiple wait actions in the same workflow to chain multiple long calls.

Initial request ref: https://community.baserow.io/t/automating-app-builder-data-source-refresh-via-api-call/6607