chore(deps): Add deny.yaml and a cargo deny CI job to check dependencies

[iamjpotts]

cargo deny checks for dependencies with vulnerabilities, vulnerability advisories, unmaintained crates, duplicate dependencies, and other issues.

• Add deny.yaml
• Add exceptions for warnings without a resolution available
• Add license line license = "MIT OR Apache-2.0" to sqlx-test crate to satisfy license checker. This license spec matches what is already in the workspace Cargo.toml file
• Change sqlx-test crate to reference sqlx crate via workspace=true rather than a path`
• Change Cargo.toml at workspace root to reference sqlx-test using its version number

[iamjpotts]

Made the tempdir -> tempfile replacement its own PR: #3006

[iamjpotts]

Moved env_logger upgrade to its own PR: #3009.

[iamjpotts]

Moved criterion crate upgrade to #3010.

[iamjpotts]

Related: #1297

[abonander]

I'm not super interested in this. Too many RUSTSEC advisories are filed for trivial things like crates being unmaintained (it's only an issue if there's also high-impact bugs and PRs aren't getting merged) and our CI breaks enough as it is. Weak features in Cargo also result in a lot of false-positives (#3211).

For issues that really matter, people are pretty quick to call them out or open a PR anyway.