Notify user when httpd or extension is out of date

[maninak]

httpd is adding a new apiVersion field under GET /node which is going to follow semver. It will begin from version 0.x.y where each breaking change release is agreed to increment x .

Source: https://radicle.zulipchat.com/#narrow/stream/369278-web/topic/breaking.20changes.20in.20HTTPD/near/436044375

We should add at least a user notification letting them know when the detected httpd version has an x (or major version number) higher than the one the extension has hardcoded it is supporting.
In this case, we should warn the user to expect reduced functionality until the extension is updated to a newer compatible version. While they wait for maintainers to publish it they could roll back to version .

Similarly, and more importantly, we should add another user notification when the extension is updated with a patch for the latest httpd but the user hasn't updated their httpd yet.
In this case we could offer a link to the website's section with the shell command to upgrade.

In either case we should offer the options "Don't show again for this version" and "Don't show again ever". The former should save its state using ExtensionContext.globalState and the latter should save its state as an extension config which by default allows notifications.
It may be a good idea to put that new config under a new group "Notifications" or something where we can also store configs to control other notifications.