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_formatter/Cargo.toml

@@ -29,3 +29,6 @@ insta = { workspace = true }
 [features]
 serde = ["dep:serde", "ruff_text_size/serde"]
 schemars = ["dep:schemars", "ruff_text_size/schemars"]
+
+[lints]
+workspace = true

crates/ruff_formatter/src/printer/mod.rs

@@ -1711,14 +1711,14 @@ mod tests {
         ));
 
         assert_eq!(
-            r#"a
+            "a
   b
     c
       d
       d
     c
   b
-a"#,
+a",
             formatted.as_code()
         );
     }
@@ -2047,10 +2047,10 @@ two lines`,
 
         assert_eq!(
             printed.as_code(),
-            r#"Group with id-2
+            "Group with id-2
 Group with id-1 does not fit on the line because it exceeds the line width of 80 characters by
 Group 2 fits
-Group 1 breaks"#
+Group 1 breaks"
         );
     }