Warm up query plan cache at boot using persisted queries

[lleadbet]

Describe the solution you'd like

With the current warmup implementation, the router will only warm up the query plan cache when it has been reloaded through a schema update (e.g. Uplink) or config update (when using --hr or --dev).

Persisted queries affords the opportunity to use known queries to prepopulate the cache prior to serving any traffic on initial boot, and should be used as such in addition to the updating logic.

Describe alternatives you've considered

Running the router in prod with --hr and sending a SIGHUP command to force a refresh.