Reduce amount of ssl related params in client API

[asvetlov]

Now we have verify_ssl, fingerprint and ssl_context.

The proposal is replacing all of them with ssl.

• if ssl is instance of ssl.SSLContext it is used as ssl_context
• if ssl is False -- verify_ssl=False logic is applied
• if ssl is instance of new Fingerprint class -- fingerprit check is applied

Existing params should be deprecated.

[asvetlov]

Fixed by #2628

[lock]

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[new issue]: https://github.com/aio-libs/aiohttp/issues/new