ices/99914.rs: fixed with errors

[github-actions]

Issue: rust-lang/rust#99914

struct Error;

fn foo() {
    let initial_exchange: Result<usize, Error> = todo!();
    initial_exchange.and_then(|_|
        serve_udp_tunnel()
    ).await;
}

async fn serve_udp_tunnel() {}

=== stdout ===
=== stderr ===
error[E0728]: `await` is only allowed inside `async` functions and blocks
 --> /home/runner/work/glacier/glacier/ices/99914.rs:7:6
  |
3 | fn foo() {
  |    --- this is not `async`
...
7 |     ).await;
  |      ^^^^^^ only allowed inside `async` functions and blocks

error[E0601]: `main` function not found in crate `99914`
  --> /home/runner/work/glacier/glacier/ices/99914.rs:10:31
   |
10 | async fn serve_udp_tunnel() {}
   |                               ^ consider adding a `main` function to `/home/runner/work/glacier/glacier/ices/99914.rs`

warning: unreachable statement
 --> /home/runner/work/glacier/glacier/ices/99914.rs:5:5
  |
4 |       let initial_exchange: Result<usize, Error> = todo!();
  |                                                    ------- any code following this expression is unreachable
5 | /     initial_exchange.and_then(|_|
6 | |         serve_udp_tunnel()
7 | |     ).await;
  | |____________^ unreachable statement
  |
  = note: `#[warn(unreachable_code)]` on by default

error[E0308]: mismatched types
  --> /home/runner/work/glacier/glacier/ices/99914.rs:6:9
   |
6  |         serve_udp_tunnel()
   |         ^^^^^^^^^^^^^^^^^^ expected enum `Result`, found opaque type
   |
note: while checking the return type of the `async fn`
  --> /home/runner/work/glacier/glacier/ices/99914.rs:10:29
   |
10 | async fn serve_udp_tunnel() {}
   |                             ^ checked the `Output` of this `async fn`, found opaque type
   = note:     expected enum `Result<_, Error>`
           found opaque type `impl Future<Output = ()>`
help: try wrapping the expression in `Ok`
   |
6  |         Ok(serve_udp_tunnel())
   |         +++                  +

error[E0277]: `Result<_, Error>` is not a future
 --> /home/runner/work/glacier/glacier/ices/99914.rs:7:6
  |
7 |     ).await;
  |      ^^^^^^ `Result<_, Error>` is not a future
  |
  = help: the trait `Future` is not implemented for `Result<_, Error>`
  = note: Result<_, Error> must be a future or must implement `IntoFuture` to be awaited
  = note: required for `Result<_, Error>` to implement `IntoFuture`
help: remove the `.await`
  |
7 -     ).await;
7 +     );
  |

error: aborting due to 4 previous errors; 1 warning emitted

Some errors have detailed explanations: E0277, E0308, E0601, E0728.
For more information about an error, try `rustc --explain E0277`.
==============