Make all dependencies workspace dependencies

[charliermarsh]

Summary

This PR modifies our Cargo.toml files to use workspace dependencies for all dependencies, rather than the status quo of sporadically trying to use workspace dependencies for those dependencies that are used across multiple crates. I find the current situation more confusing and harder to manage, since we have a mix of workspace and crate-local dependencies, whereas this setup consistently uses the same approach for all dependencies.

[github-actions]

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[konstin]

Big 👍 keeping all the [dependencies] tables consistent. One disadvantage is that this pulls [dev-dependencies] and ruff_dev into [workspace.dependencies], so the top level dependency table contains crates that the ruff binary doesn't require, e.g. tempfile and imara-diff (that's not our diff library, we use similar, only ruff_dev uses imara-diff for perf reasons).

[charliermarsh]

👍 Makes sense -- maybe I'll move ruff_dev to use non-workspace dependencies for everything, actually.

[charliermarsh]

Hmm, I started to do this (move all dev dependencies out of the workspace) but then kinda changed my mind. It still seems good to have them use consistent declarations.

[BurntSushi]

I like this. I was also unsure of when to add something as a workspace dep and when not to.