Update to Rust 1.74 and use new clippy lints table (#8722)

Update to [Rust
1.74](https://blog.rust-lang.org/2023/11/16/Rust-1.74.0.html) and use
the new clippy lints table.

The update itself introduced a new clippy lint about superfluous hashes
in raw strings, which got removed.

I moved our lint config from `rustflags` to the newly stabilized
[workspace.lints](https://doc.rust-lang.org/stable/cargo/reference/workspaces.html#the-lints-table).
One consequence is that we have to `unsafe_code = "warn"` instead of
"forbid" because the latter now actually bans unsafe code:

```
error[E0453]: allow(unsafe_code) incompatible with previous forbid
  --> crates/ruff_source_file/src/newlines.rs:62:17
   |
62 |         #[allow(unsafe_code)]
   |                 ^^^^^^^^^^^ overruled by previous forbid
   |
   = note: `forbid` lint level was set on command line
```

---------

Co-authored-by: Charlie Marsh <charlie.r.marsh@gmail.com>

crates/ruff_python_formatter/Cargo.toml

@@ -55,3 +55,6 @@ required-features = ["serde"]
 default = ["serde"]
 serde = ["dep:serde", "ruff_formatter/serde", "ruff_source_file/serde", "ruff_python_ast/serde"]
 schemars = ["dep:schemars", "ruff_formatter/schemars"]
+
+[lints]
+workspace = true