Reduce hyper dependency

[tottoto]

Motivation

Reduces hyper dependency.

Solution

Depends on hyper only when it is used.

[jplatte]

You are implicitly creating a hyper feature by not using dep: syntax for the feature dependency. I don't think that is what we want, right? I also wonder if any of the features that enable hyper + one of its features should be made to not enable hyper. Would have to be reviewed one by one.

[tottoto]

Fixed the implicit feature, caused by missing dep: prefix.

[tottoto]

The mix use of dep:crate and crate/feature seems to need to be waited until Rust 1.71. So changing hyper optional dependency does not seem possible at the moment.

[jplatte]

Yes, "dep:hyper" and "hyper/foo" can't be mixed in older versions but you can just write "dep:hyper", "hyper?/foo", which has the same meaning as "hyper/foo".

[tottoto]

Thanks. Fixed to use the workaround.