build: Do not rely on RUSTFLAGS for Clippy lint configuration

[Xanewok]

Since Rust 1.74 it's possible to configure lints directly in the Cargo.toml rather than relying on setting custom RUSTFLAGS: https://blog.rust-lang.org/2023/11/16/Rust-1.74.0.html#lint-configuration-through-cargo.

Setting RUSTFLAGS is fragile as there are some corner cases to look out for, like:

1. it being exclusive with other sources of flags e.g. overwriting build.rustflags or target.<cfg>.rustflags or
2. forcing a separate rebuild whenever the flags change, preventing the reuse of build cache in common cases (e.g. for a regular build vs one with warnings denied).

See NomicFoundation/slang#880 for what we did for Slang.

This also changes the pre-commit hook to not rely/set the flag and only runs clippy, rather than check + clippy, which seems wasteful in this case, as cargo clippy already runs the underlying rustc machinery for compilation checks.

[changeset-bot]

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Latest commit: 74a9014

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[Xanewok]

https://github.com/NomicFoundation/edr/actions/runs/9415777943/job/25937468081?pr=499 seems spurious, retrying:

 Alchemy Forked provider
         "before each" hook: Initialize provider for "Supports single and batched requests":
     Error: Timeout of 50000ms exceeded. For async tests and hooks, ensure "done()" is called; if returning a Promise, ensure it resolves. (/Users/runner/work/edr/edr/hardhat-tests/test/internal/hardhat-network/provider/modules/eth/websocket.ts)

[Wodann]

One nice-to-have. Otherwise looks good to me.

For next time, please make sure to assign reviewers to your PR. That way people get a more obvious notification and will likely review quicker :)

[Wodann]

Nice to have: alphabetic ordering

[Xanewok]

Done in 74a9014. thanks!