Drop tokio dependency

[jbaum98]

Now that hyper uses its own traits instead of tokios (#3110, #3230), the only place that tokio is used is to provide tokio::sync::oneshot::Receiver in src/upgarde.rs. If we could find a way to implement this functionality without tokio's oneshot, we could drop the dependency entirely. This would have a pretty huge impact on the transitive dependencies we pull in everywhere hyper is used: from this:

hyper v1.5.0 (/home/jake/tmp/hyper)
├── bytes v1.7.2
├── http v1.1.0
│   ├── bytes v1.7.2
│   ├── fnv v1.0.7
│   └── itoa v1.0.11
├── http-body v1.0.1
│   ├── bytes v1.7.2
│   └── http v1.1.0 (*)
└── tokio v1.40.0
    ├── bytes v1.7.2
    ├── libc v0.2.161
    ├── mio v1.0.2
    │   └── libc v0.2.161
    ├── pin-project-lite v0.2.14
    ├── socket2 v0.5.7
    │   └── libc v0.2.161
    └── tokio-macros v2.4.0 (proc-macro)
        ├── proc-macro2 v1.0.88
        │   └── unicode-ident v1.0.13
        ├── quote v1.0.37
        │   └── proc-macro2 v1.0.88 (*)
        └── syn v2.0.80
            ├── proc-macro2 v1.0.88 (*)
            ├── quote v1.0.37 (*)
            └── unicode-ident v1.0.13

to this:

hyper v1.5.0
├── bytes v1.7.2
├── http v1.1.0
│   ├── bytes v1.7.2
│   ├── fnv v1.0.7
│   └── itoa v1.0.11
└── http-body v1.0.1
    ├── bytes v1.7.2
    └── http v1.1.0 (*)

I also think this would make hyper more appealing to use with other executors like smol @notgull.