rust: update cluster management examples to use new API

[danielfrankcom]

This change updates the Rust cluster management examples as follows:

• Use new AWS SDK for multi-region management
• Standardize examples based on AWS docs
• Clean up documentation
• Separate standalone binaries from tests
• Add formatting check to workflow
• Add binary execution check to workflow

By submitting this pull request, I confirm that my contribution is made under the terms of the MIT-0 license.

[trstephen-amazon]

No blockers. Left some optional points you can address at your discretion, or merge.

[danielfrankcom]

• f4af901 addresses most active comments.
• 1f86c9a updates the CI job to check all standalone binaries, and increases the job timeout for the test run from 15 mins to 30 due to a recent failure.

[danielfrankcom]

• 49e66f6 makes the binary check job more permissive about the env var which is checked for

[danielfrankcom]

• ffc9d37 updates the wording of the messages during the binary check

[trstephen-amazon]

I'm OK with this as-is. Still not convinced of the binary poking in CI but it's very unlikely to be a burden.