Fix clippy warnigs and make CI fail upon clippy warnings

[clangenb]

No description provided.

[brenzi]

for the node? I think parity does not use clippy, so this work might be high-maintenance. Or is upstream clippified by now?

[clangenb]

No they still don't. While doing the integritee-parachain I realized why; parity's code is to complex and clippy reports many false positives.

I predominantly meant the client. We run clippy there, but the CI does not fail yet (and clippy reports many warnings).

I will check the node, if it is too much I skip it.