Add support for preQueryPlugin to be async about ddf

[willwill96]

Updated the description 😄
As for shared resources/state, etc., the main concern is making sure that the new return value (was an array but now is a promise) is handled gracefully.
Parallel plugins should not be an issue as the preQueryPlugin in the frontend is a single function, and if you start a new query, the old one will be deleted, meaning there will never be multiple operating simultaneously. Any implementation that operates differently is up to downstream projects to work out the kinks.

[coyotesqrl]

Is this a proposed change to make all pre-query plugins run asynchronously or to be able to in some way indicate that a specific implementation of the service should be run async?

Does this imply that the framework can fire off N pre-query plugins to run in parallel and then wait before moving onto the next processing step? Would there be a timeout for these async operations? Would it be a failure condition if any of the async plugins didn't complete before timing out or would that be a logged warning and the query process would continue?

Are there any concerns about async plugins stepping on each other during parallel processing? Would there be any mechanism in place to protect shared resources and state?

[coyotesqrl]

I see from quickly glancing at the PR that's gone up against this issue that it is UI related and does not impact PreQueryPlugins in the catalog. As that wasn't clear, I think this issue needs a bit more meat in the description to clarify the use cases.

Also, some of my earlier questions - regarding shared resources/state, timeouts, and failures of individual plugins - still seem relevant.