Make the auto-generated release note tables/sections configurable

[Gankra]

At very least you should be able to turn them off.

[ashleygwilliams]

re: configuration for the display- i think turning them off as a feature makes sense.

re: configuring how they are displayed- i think for cargo-dist i would only want it to store configuration for metadata for releases and not for display- so to the extent that the display can really be understood as release metadata, i'm ok with it- but otherwise we may be talking about a new tool.

re: what i mean about release metadata- let's say people want to emphasize or prioritize a particular artifact and/or warn about one. instead of this being a "display" feature, we could make it an attribute on the release "preferred" or "unstable". curious if that make sense?

[Gankra]

another data point: zkat thinks release notes should Come First. I think that might just be a good new Default tho.