Make RetryIfFunc handle request errors

[ksw2000]

Fix #1744
To maintain compatibility with the previous RetryIfFunc as much as possible, I think it can be relaxed into an interface{} type.
I believe that directly adding an extra field might confuse developers.
If we were to directly use generics introduced in Go 1.18 for type constraints, it would involve too many changes.
I think the most balanced approach for now is to handle it using interface{} and type assertion.

[erikdubbelboer]

I have been thinking about this, and I think it's too much of a backwards incompatible change also also makes it less clear on how to use it. I would suggest we add a RetryIfError func(request *Request) bool and mark RetryIf as deprecated.

[erikdubbelboer]

Thanks!

[ksw2000]

Oops, I found that I only added the new field for HostClient but not for Client.

@erikdubbelboer what should I do? Create a new PR?