Logging for unsupported Node versions

[danielleadams]

Issue

If an app starts using a new Node version that is not yet supported by the Node metrics plugin, Node metrics silently disables metrics without explaining why.

Expected

There should be some logging that advises the user that the Node version is unsupported and metrics will be disabled. (Also, more closely released versions with plugins would be helpful, but we should still let the user know in that timeframe)

[johlym]

Dropping by to add a comment on this because it has come up in a recent support ticket. Should this check and message instead take place in the Node.js buildpack? (specifically, here)