Remove crypto's pimpl idiom

[anonimal]

We don't need it, I never wanted it, it's annoying to deal with and it's unneeded overhead. Crypto++ is a fine library of which I've worked side-by-side with and I don't foresee it leaving anytime soon. We also don't change our crypto enough to warrant a pimpl design so, simply treating our implementation file(s) as implementation files should suffice - without the need for pimpl.

Removing pimpl won't prevent us from changing libraries. If we end up changing any interfaces in the process of resolving this issue, the changes will be for the better.

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[anonimal]

NOTICE: THIS ISSUE HAS BEEN MOVED TO GitLab. Please continue the discussion there. See #1013 for details.