Upgrade to Rust 1.86 and bump MSRV to 1.84 (#17171)

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## Summary

I decided to disable the new
[`needless_continue`](https://rust-lang.github.io/rust-clippy/master/index.html#needless_continue)
rule because I often found the explicit `continue` more readable over an
empty block or having to invert the condition of an other branch.


## Test Plan

`cargo test`

---------

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>

crates/ruff_python_formatter/src/comments/placement.rs

@@ -273,7 +273,7 @@ fn handle_enclosed_comment<'a>(
                     .any(|token| token.kind() == SimpleTokenKind::LBracket)
                 {
                     return CommentPlacement::Default(comment);
-                };
+                }
 
                 // If there are no additional tokens between the open parenthesis and the comment, then
                 // it should be attached as a dangling comment on the brackets, rather than a leading
@@ -1393,7 +1393,7 @@ fn handle_attribute_comment<'a>(
     {
         if comment.start() < right_paren.start() {
             return CommentPlacement::trailing(attribute.value.as_ref(), comment);
-        };
+        }
     }
 
     // If the comment precedes the `.`, treat it as trailing _if_ it's on the same line as the
@@ -1648,7 +1648,7 @@ fn handle_pattern_match_mapping_comment<'a>(
     // like `rest` above, isn't a node.)
     if comment.following_node().is_some() {
         return CommentPlacement::Default(comment);
-    };
+    }
 
     // If there's no rest pattern, no need to do anything special.
     let Some(rest) = pattern.rest.as_ref() else {

crates/ruff_python_formatter/src/comments/visitor.rs

@@ -363,7 +363,7 @@ pub(super) enum CommentPlacement<'a> {
     /// Makes the comment a...
     ///
     /// * [trailing comment] of the [`preceding_node`] if both the [`following_node`] and [`preceding_node`] are not [None]
-    ///     and the comment and [`preceding_node`] are only separated by a space (there's no token between the comment and [`preceding_node`]).
+    ///   and the comment and [`preceding_node`] are only separated by a space (there's no token between the comment and [`preceding_node`]).
     /// * [leading comment] of the [`following_node`] if the [`following_node`] is not [None]
     /// * [trailing comment] of the [`preceding_node`] if the [`preceding_node`] is not [None]
     /// * [dangling comment] of the [`enclosing_node`].