Can't specify both fingerprint and SSLContext for client request

## Long story short

It appears that 4.0 will remove all the SSL parameters from the `TCPConnector` class except for a single `ssl` parameter (#2626). This appears to be quite limiting: for example, it would no longer be possible to supply a client certificate and simultaneously pin the expected server certificate. The former requires you to pass the `SSLContext` configured with the client certificate as the `ssl` parameter, but for the latter you would have to pass a `Fingerprint`. Is there a recommendation for how this could be achieved?

## Expected behaviour

Should be possible to make a request with BOTH a client certificate and a pinned server certificate.

## Actual behaviour

It appears this will be removed with no alternative offered in 4.0.

## Steps to reproduce

N/A

## Your environment

client