Configuring `[workspace.lints.clippy]` in workspace-level Cargo.toml files

[tarcieri]

Perhaps we can put together a set of clippy lints we want to apply everywhere and start setting these at the workspace level in Cargo.toml.

clippy::restriction lints seem particularly interesting, e.g. mod_module_files

[newpavlov]

Sounds interesting.

[tarcieri]

missing_debug_impls and missing_docs might be good lints to apply at a workspace level