remove several uses of unsafe (#8600)

This PR removes several uses of `unsafe`. I generally limited myself to
low hanging fruit that I could see. There are still a few remaining uses
of `unsafe` that looked a bit more difficult to remove (if possible at
all). But this gets rid of a good chunk of them.

I put each `unsafe` removal into its own commit with a justification for
why I did it. So I would encourage reviewing this PR commit-by-commit.
That way, we can legislate them independently. It's no problem to drop a
commit if we feel the `unsafe` should stay in that case.

crates/ruff_formatter/src/macros.rs

@@ -329,10 +329,8 @@ macro_rules! format {
 #[macro_export]
 macro_rules! best_fitting {
     ($least_expanded:expr, $($tail:expr),+ $(,)?) => {{
-        #[allow(unsafe_code)]
-        unsafe {
-            $crate::BestFitting::from_arguments_unchecked($crate::format_args!($least_expanded, $($tail),+))
-        }
+        // OK because the macro syntax requires at least two variants.
+        $crate::BestFitting::from_arguments_unchecked($crate::format_args!($least_expanded, $($tail),+))
     }}
 }