Omit autonat and kad features from the web-client

[sisou]

What's in this pull request?

Improve usage of feature flags throughout different crates to avoid bundling autonat and parts of kad functionality into the web-client (and I believe thus light client, too)

Pull request checklist

• All tests pass. The project builds and runs.
• I have resolved any merge conflicts.
• I have resolved all clippy and rustfmt warnings.

[Eligioo]

I would prefer to fix this by creating a new 'light' behaviour and gate that based on the target platform here instead of adding all these feature flags. It makes everything quite messy and difficult to maintain now.

This new light behaviour would omit all the stuff(autonat, kad, etc.) that are not necessary for a light client.

PR #3012 prepped this effort by detaching the events from the handlers.

[sisou]

OK fair enough, but I don't know anything about how that works, so someone else will have to tackle it. Is it a huge effort?