Offload potentially expensive query planning steps to async tasks.

[apmoriarty]

Although the metadata helper is supposed to cache expensive method calls, this does not always work out in a production environment. Many of these expensive calls can be executed in parallel, thus reducing the setup time for a query.

• Offloaded potentially expensive method calls to async tasks.
• updated some planner method interfaces
• optionally log timed saved via async execution

[mineralntl]

LGTM other than possibly condensing a few methods but that's just personal preference