chore: prepare tokio-util 0.7.1 release (tokio-rs#4521)

# 1.17.0 (February 16, 2022)

This release updates the minimum supported Rust version (MSRV) to 1.49,
the `mio` dependency to v0.8, and the (optional) `parking_lot`
dependency to v0.12. Additionally, it contains several bug fixes, as
well as internal refactoring and performance improvements.

### Fixed

- time: prevent panicking in `sleep` with large durations ([tokio-rs#4495])
- time: eliminate potential panics in `Instant` arithmetic on platforms
  where `Instant::now` is not monotonic ([tokio-rs#4461])
- io: fix `DuplexStream` not participating in cooperative yielding
  ([tokio-rs#4478])
- rt: fix potential double panic when dropping a `JoinHandle` ([tokio-rs#4430])

### Changed

- update minimum supported Rust version to 1.49 ([tokio-rs#4457])
- update `parking_lot` dependency to v0.12.0 ([tokio-rs#4459])
- update `mio` dependency to v0.8 ([tokio-rs#4449])
- rt: remove an unnecessary lock in the blocking pool ([tokio-rs#4436])
- rt: remove an unnecessary enum in the basic scheduler ([tokio-rs#4462])
- time: use bit manipulation instead of modulo to improve performance
  ([tokio-rs#4480])
- net: use `std::future::Ready` instead of our own `Ready` future
  ([tokio-rs#4271])
- replace deprecated `atomic::spin_loop_hint` with `hint::spin_loop`
  ([tokio-rs#4491])
- fix miri failures in intrusive linked lists ([tokio-rs#4397])

### Documented

- io: add an example for `tokio::process::ChildStdin` ([tokio-rs#4479])

### Unstable

The following changes only apply when building with `--cfg
tokio_unstable`:

- task: fix missing location information in `tracing` spans generated by
  `spawn_local` ([tokio-rs#4483])
- task: add `JoinSet` for managing sets of tasks ([tokio-rs#4335])
- metrics: fix compilation error on MIPS ([tokio-rs#4475])
- metrics: fix compilation error on arm32v7 ([tokio-rs#4453])

[tokio-rs#4495]: tokio-rs#4495
[tokio-rs#4461]: tokio-rs#4461
[tokio-rs#4478]: tokio-rs#4478
[tokio-rs#4430]: tokio-rs#4430
[tokio-rs#4457]: tokio-rs#4457
[tokio-rs#4459]: tokio-rs#4459
[tokio-rs#4449]: tokio-rs#4449
[tokio-rs#4462]: tokio-rs#4462
[tokio-rs#4436]: tokio-rs#4436
[tokio-rs#4480]: tokio-rs#4480
[tokio-rs#4271]: tokio-rs#4271
[tokio-rs#4491]: tokio-rs#4491
[tokio-rs#4397]: tokio-rs#4397
[tokio-rs#4479]: tokio-rs#4479
[tokio-rs#4483]: tokio-rs#4483
[tokio-rs#4335]: tokio-rs#4335
[tokio-rs#4475]: tokio-rs#4475
[tokio-rs#4453]: tokio-rs#4453

chore: prepare tokio-util 0.7.0 (tokio-rs#4486)

chore: specify tokio-macros version (tokio-rs#4455)

chore: prepare Tokio 1.8.5 release

chore: prepare Tokio v1.16.1 release (tokio-rs#4438)

chore: prepare Tokio v1.16 release (tokio-rs#4431)

chore: prepare Tokio v1.15.0 release (tokio-rs#4320)

Includes `tokio-macros` v1.7.0

chore: prepare Tokio v1.15.0 release (tokio-rs#4320)

Includes `tokio-macros` v1.7.0

chore: prepare tokio-macros 1.6.0 (tokio-rs#4239)