Update Rust dependencies

[tjkirch]

Description of changes:

11abc457 tools: use tokio LTS release series 1.8.x
bd7bd6e7 tools: update rusoto to 0.47.0
ed019543 tools: cargo update
3e955937 sources: use tokio LTS release series 1.8.x
e73eb6fb sources: update rusoto to 0.47.0
d77bf5ef sources: cargo update
bd015cb0 sources: update nix to 0.22.0

Not updated: gptman, hyper (in sources/), argh, and handlebars, which is a major version update I'm handling separately.

Testing done:

Unit tests pass. Built k8s 1.19 and ECS AMIs for x86_64 and aarch64. Confirmed systemctl status running, dmesg and journal OK. Ran a pod/task OK. Made API changes OK.

Confirmed that cargo make repo and cargo make ssm still work OK.

Terms of contribution:

By submitting this pull request, I agree that this contribution is dual-licensed under the terms of both the Apache License, version 2.0, and the MIT license.

[tjkirch]

^ Rebase on develop to fix conflict from #1654.