Remove (most) local use declarations in tokio::select!

[iriri]

Motivation

Some of the use declarations in tokio::select! shadow common names. See #7928 for a reproduction of the issue.

Solution

Using fully qualified paths avoids unnecessary imports. We unfortunately have to leave the Pin import untouched, however, as some downstream crates (likely unknowingly) depend on it being implicitly brought into scope.

[martin-g]

Using fully qualified paths is the more principled solution, but it results in some very long lines. I am perfectly happy to switch to that solution however.

Looking at the diff I think it won't lead to very long lines in this case.
+1 for fully qualified paths!

[iriri]

   Compiling hyper v1.8.1 (/home/runner/work/tokio/tokio/hyper)
error[E0433]: failed to resolve: use of undeclared type `Pin`
   --> examples/upgrades.rs:166:40
    |
166 |                         let mut conn = Pin::new(&mut conn);
    |                                        ^^^ use of undeclared type `Pin`
    |
help: consider importing this struct

Wow, there's downstream code that depends on these declarations existing. That's unfortunate to say the least. We may have to leave Pin unchanged.

[Darksonn]

Looks okay to me. The Pin one is unfortunate, but ok let's keep it.