Consolidate dependency version management

[nyurik]

• Consolidate MSRV management, and automate CI to pick it from the Cargo.toml instead of hardcoding
• Consolidate Rust language edition management
• Consolidate dependency management

With workspaces we can consolidate all dependency management in one location. Even if dependency is used only once, we do not need to track if it is being used only once, plus we don't need to move things to a central places when more than one place uses it. This keeps things much simpler, and ensures that every single dependency is listed in one location.