Add tests verifying existence of some interfaces. · google/rrg@1a39af0

The following actions uses node12 which is deprecated and will be forced to run on node16: actions/checkout@v2, actions-rs/toolchain@v1, actions-rs/cargo@v1. For more info: https://github.blog/changelog/2023-06-13-github-actions-all-actions-will-run-on-node16-instead-of-node12-by-default/

some crates are on edition 2021 which defaults to `resolver = "2"`, but virtual workspaces default to `resolver = "1"`

unused import: `std::thread::sleep`

unused import: `std::time::Duration`

`rrg` (lib test) generated 2 warnings (run `cargo fix --lib -p rrg --tests` to apply 2 suggestions)

The `set-output` command is deprecated and will be disabled soon. Please upgrade to using Environment Files. For more information see: https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

some crates are on edition 2021 which defaults to `resolver = "2"`, but virtual workspaces default to `resolver = "1"`

Provide feedback