fix: client typing changes to accommodate JSON lists

[jtsextonMITRE]

Closes #836

[jkglasbrenner]

This PR was impacted by many of the recent changes to dev, and resolving it looks messy. Just getting this back in sync might require that we carefully reapply changes to a new branch from dev at this point.

More generally, this is still on my radar, but I really want to be careful with how we're solving this and think through whether the approach in this PR is what we actually want. The outcome we want is straightforward, we want to be able to express that the JSON version of the client can return more than just the dict[str, Any] type, since for example list[dict[str, Any]] and list[str | int | float | None] are also valid JSON that json.loads will handle properly. Just using dict[str, Any] | list[Any] | None is not a proper solution because we don't want to force client users to validate the returned type everywhere. The challenge I'm seeing is that the more specific we want to be with our returned types so that we can avoid post-call checks, such that we can say a method returns list[str] rather than list[Any], the more complex it will be to express this using static types and generics. Right now we've tried to address this by adding a second general type everywhere that each method can pick from. However, if we reserve it for something like list[dict[str, Any]], it still excludes list[str | int | float | None], and there can be cases where we'd want the list of scalars like that. I want to make sure that how this is done is expressed at the right level of abstraction, rather than what just seemed to be the quickest patch we could find.