build: enable the build:dns-fallback step from npm run generate

[jnsgruk]

This PR is broken into a few commits:

1. Ignore the paths of the new snapcraft remote-build logs
2. Enable a build step we were previously skipping due to proxy issues; this required an actual patch to the source, which I will propose upstream
3. Remove some older build patterns/cleanup stuff
4. Add the x11/wayland plugs - not sure why these weren't already in!

[merlijn-sebrechts]

I'm surprised you're removing the cleanup part. Is there no size difference anymore?

Secondly, I think the app has too many plugs, not too little. The extension already adds a bunch of plugs. You can see the resulting yaml with snapcraft expand-extensions. Or am I missing something?

[jnsgruk]

@merlijn-sebrechts indeed - I've removed the ones already bought in by the extension in a later commit. Should be good now.

There is no size difference, I believe a lot more of this is taken care of automatically by the extension now.