hyper-util's "client-legacy" feature forces use of mio, but wasn't required in hyper 0.14.x

Version List the version(s) of hyper, and any relevant hyper dependency (such as h2 if this is related to HTTP/2).

hyper 1.6.0, hyper-util 0.1.10

Platform The output of uname -a (UNIX), or version and 32 or 64-bit (Windows)

Fuchsia

Description Enter your issue details here. One way to structure the description:

I work on the Fuchsia operating system, and we're running into problems updating hyper from 0.14.x to 1.x with this in our Cargo.toml:

hyper = { version = "0.14.19", default-features = false, features = ["stream", "http1", "client", "server"] }
hyper-rustls = { version = "0.24.2", default-features = false }
...

This is requiring us to also update our hyper-rustls from 0.24.2 to 0.27.5, which now depends on hyper-util 0.1.x to wrap the client library. This causes our version of tokio to enable the mio feature, which doesn't support Fuchsia and fails to compile.

From what I can tell, this worked back in hyper 0.14.x because these subset of feature flags allowed hyper-rustls 0.24.x to expose most of it's functionality it needed based off the lower level connection API. It seems that hyper-util 0.1.10's client-legacy feature merged that functionality together that requires tokio. Would it be possible to restore this old functionality? It'd be unfortunate for us to have to essentially fork hyper-rustls and hyper-util to allow it to work with a non-tokio executor. I'd be happy to help with a refactor there's interest in this.