Centrally manage all dependencies as workspace dependencies

[heaths]

• [ ] Move all HLC dependencies to root Cargo.toml in [workspace.dependencies].
• [ ] Update code generator to use inherited dependencies.
• [x] Add validation to make sure new package-level dependencies aren't defined, possibly as a clippy lint.

[heaths]

Given a healthy discussion within the Rust community, we may need to write validation as a standalone executable we can run in pipelines. Simplistically, it just needs to deserialize Cargo.toml (use cargo_util_schemas with serde) for individual crates and make sure all dependencies (see list below) use workspace = true.

• dependencies
• dev-dependencies
• build-dependencies
• regex: ^target\..*\.(dev-|build-)?dependencies$