build error on main due to tokio 1.21.0 unstable feature

[redshiftzero]

Build error just occurred on main when I merged #1328, probably unrelated?

err:    Compiling console-subscriber v0.1.7
err: error[E0308]: mismatched types
err:     --> /***/.cargo/registry/src/github.com-1ecc6299db9ec823/console-subscriber-0.1.7/src/lib.rs:1066:12
err:      |
err: 1061 | ) -> tokio::task::JoinHandle<T>
err:      |      -------------------------- expected `tokio::task::JoinHandle<T>` because of return type
err: ...
err: 1066 |     return tokio::task::Builder::new().name(_name).spawn(task);
err:      |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `tokio::task::JoinHandle`, found enum `Result`
err:      |
err:      = note: expected struct `tokio::task::JoinHandle<_>`
err:                   found enum `Result<tokio::task::JoinHandle<_>, std::io::Error>`
err: 
err: For more information about this error, try `rustc --explain E0308`.
err: error: could not compile `console-subscriber` due to previous error
err: warning: build failed, waiting for other jobs to finish...
err: error: build failed

[redshiftzero]

Hypothesis: this is due to release of tokio 1.21.0 in the last 24 hours (https://github.com/tokio-rs/tokio/releases/tag/tokio-1.21.0) which includes tokio-rs/tokio#4823

[hdevalence]

That looks right, seems like it should be an easy fix to patch our use of the API?

[redshiftzero]

Cross linking tokio-rs/console#373

There are also some related build errors in our view crate which we can fix, though the console-subscriber API change we'll need updated, so in #1358 I'm gonna pin us to the old version for now