fix: Change default ConfigReloadInterval, add jitter, fix docs

[kentquirk]

Which problem is this PR solving?

• The default config reload interval was too long, and the documentation for it was wrong.

Short description of the changes

• Change default for config reload to 15s from 5m. The original intent (see Allow peers to gossip news of a new config #725) was to have a fleet of refineries gossiping news of new configs, but that's tricky to get right and probably not needed, especially since for now at least, almost all installations will be using a config file, not a config url.
• Add a random jitter to avoid thundering herds.
• Update metadata to explain what it's really doing
• Regenerate documentation.

[TylerHelmuth]

@kentquirk once this is merged can you open an issue for the helm chart so we remember to update the default values.yaml to set this to 0s?