In preparation for #3541, I'm improving the way dependencies are managed across the windows-rs repo by leveraging the workspace Cargo.toml to define all dependencies. This way, any time a crate's version is updated, it doesn't require that change to be repeated throughout the repo.

Cargo still requires that the crate's version be specified in both the crate's Cargo.toml file as well as the workspace Cargo.toml file, but the latter is now updated automatically by tool_workspace. This should make release management far less error-prone.

This update also introduces tool_test_all for locally testing all crates individually. cargo test --all does a great job in general. The problem is that Cargo will try and optimize the build by aggregating all of the features required by all crates and thus does not catch the case when a particular crate depends on a feature that was not explicitly requested by that crate. Running tool_test_all will catch those. This is already done by the test.yml but tool_test_all just makes it easier to catch such mistakes locally before creating a PR.