Update Rust crate tokio to 1.20 (#99)

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This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [tokio](https://tokio.rs) ([source](https://togithub.com/tokio-rs/tokio)) | dependencies | minor | `1.19` -> `1.20` |

---

### Release Notes

<details>
<summary>tokio-rs/tokio</summary>

### [`v1.20.0`](https://togithub.com/tokio-rs/tokio/releases/tag/tokio-1.20.0)

[Compare Source](https://togithub.com/tokio-rs/tokio/compare/tokio-1.19.2...tokio-1.20.0)

##### 1.20.0 (July 12, 2022)

##### Added

-   tokio: add track_caller to public APIs ([#&#8203;4772], [#&#8203;4791], [#&#8203;4793], [#&#8203;4806], [#&#8203;4808])
-   sync: Add `has_changed` method to `watch::Ref` ([#&#8203;4758])

##### Changed

-   time: remove `src/time/driver/wheel/stack.rs` ([#&#8203;4766])
-   rt: clean up arguments passed to basic scheduler ([#&#8203;4767])
-   net: be more specific about winapi features ([#&#8203;4764])
-   tokio: use const initialized thread locals where possible ([#&#8203;4677])
-   task: various small improvements to LocalKey ([#&#8203;4795])

##### Fixed

##### Documented

-   fs: warn about performance pitfall ([#&#8203;4762])
-   chore: fix spelling ([#&#8203;4769])
-   sync: document spurious failures in oneshot ([#&#8203;4777])
-   sync: add warning for watch in non-Send futures ([#&#8203;4741])
-   chore: fix typo ([#&#8203;4798])

##### Unstable

-   joinset: rename `join_one` to `join_next` ([#&#8203;4755])
-   rt: unhandled panic config for current thread rt ([#&#8203;4770])

[#&#8203;4677]: https://togithub.com/tokio-rs/tokio/pull/4677

[#&#8203;4741]: https://togithub.com/tokio-rs/tokio/pull/4741

[#&#8203;4755]: https://togithub.com/tokio-rs/tokio/pull/4755

[#&#8203;4758]: https://togithub.com/tokio-rs/tokio/pull/4758

[#&#8203;4762]: https://togithub.com/tokio-rs/tokio/pull/4762

[#&#8203;4764]: https://togithub.com/tokio-rs/tokio/pull/4764

[#&#8203;4766]: https://togithub.com/tokio-rs/tokio/pull/4766

[#&#8203;4767]: https://togithub.com/tokio-rs/tokio/pull/4767

[#&#8203;4769]: https://togithub.com/tokio-rs/tokio/pull/4769

[#&#8203;4770]: https://togithub.com/tokio-rs/tokio/pull/4770

[#&#8203;4772]: https://togithub.com/tokio-rs/tokio/pull/4772

[#&#8203;4777]: https://togithub.com/tokio-rs/tokio/pull/4777

[#&#8203;4791]: https://togithub.com/tokio-rs/tokio/pull/4791

[#&#8203;4793]: https://togithub.com/tokio-rs/tokio/pull/4793

[#&#8203;4795]: https://togithub.com/tokio-rs/tokio/pull/4795

[#&#8203;4798]: https://togithub.com/tokio-rs/tokio/pull/4798

[#&#8203;4806]: https://togithub.com/tokio-rs/tokio/pull/4806

[#&#8203;4808]: https://togithub.com/tokio-rs/tokio/pull/4808

### [`v1.19.2`](https://togithub.com/tokio-rs/tokio/compare/tokio-1.19.1...tokio-1.19.2)

[Compare Source](https://togithub.com/tokio-rs/tokio/compare/tokio-1.19.1...tokio-1.19.2)

### [`v1.19.1`](https://togithub.com/tokio-rs/tokio/compare/tokio-1.19.0...tokio-1.19.1)

[Compare Source](https://togithub.com/tokio-rs/tokio/compare/tokio-1.19.0...tokio-1.19.1)

</details>

---

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Cargo.lock

@@ -17,7 +17,7 @@ serde = "1.0"
 serde_yaml = "0.8"
 snafu = "0.7"
 strum = { version = "0.24.1", features = ["derive"] }
-tokio = { version = "1.19", features = ["macros", "rt-multi-thread"] }
+tokio = { version = "1.20", features = ["macros", "rt-multi-thread"] }
 tracing = "0.1"
 tracing-futures = { version = "0.2", features = ["futures-03"] }