Remove AstNode and AnyNode (#15479)

While looking into potential AST optimizations, I noticed the `AstNode`
trait and `AnyNode` type aren't used anywhere in Ruff or Red Knot. It
looks like they might be historical artifacts of previous ways of
consuming AST nodes?

- `AstNode::cast`, `AstNode::cast_ref`, and `AstNode::can_cast` are not
used anywhere.
- Since `cast_ref` isn't needed anymore, the `Ref` associated type isn't
either.

This is a pure refactoring, with no intended behavior changes.

crates/ruff_python_formatter/src/comments/debug.rs

@@ -184,7 +184,7 @@ mod tests {
     use insta::assert_debug_snapshot;
 
     use ruff_formatter::SourceCode;
-    use ruff_python_ast::AnyNode;
+    use ruff_python_ast::AnyNodeRef;
     use ruff_python_ast::{StmtBreak, StmtContinue};
     use ruff_python_trivia::{CommentLinePosition, CommentRanges};
     use ruff_text_size::{TextRange, TextSize};
@@ -194,13 +194,13 @@ mod tests {
 
     #[test]
     fn debug() {
-        let continue_statement = AnyNode::from(StmtContinue {
+        let continue_statement = StmtContinue {
             range: TextRange::new(TextSize::new(18), TextSize::new(26)),
-        });
+        };
 
-        let break_statement = AnyNode::from(StmtBreak {
+        let break_statement = StmtBreak {
             range: TextRange::new(TextSize::new(55), TextSize::new(60)),
-        });
+        };
 
         let source = r"# leading comment
 continue; # trailing
@@ -213,7 +213,7 @@ break;
         let mut comments_map: CommentsMap = MultiMap::new();
 
         comments_map.push_leading(
-            continue_statement.as_ref().into(),
+            AnyNodeRef::from(&continue_statement).into(),
             SourceComment::new(
                 source_code.slice(TextRange::at(TextSize::new(0), TextSize::new(17))),
                 CommentLinePosition::OwnLine,
@@ -221,7 +221,7 @@ break;
         );
 
         comments_map.push_trailing(
-            continue_statement.as_ref().into(),
+            AnyNodeRef::from(&continue_statement).into(),
             SourceComment::new(
                 source_code.slice(TextRange::at(TextSize::new(28), TextSize::new(10))),
                 CommentLinePosition::EndOfLine,
@@ -229,7 +229,7 @@ break;
         );
 
         comments_map.push_leading(
-            break_statement.as_ref().into(),
+            AnyNodeRef::from(&break_statement).into(),
             SourceComment::new(
                 source_code.slice(TextRange::at(TextSize::new(39), TextSize::new(15))),
                 CommentLinePosition::OwnLine,

crates/ruff_python_formatter/src/comments/format.rs

@@ -1,7 +1,7 @@
 use std::borrow::Cow;
 
 use ruff_formatter::{format_args, write, FormatError, FormatOptions, SourceCode};
-use ruff_python_ast::{AnyNodeRef, AstNode, NodeKind, PySourceType};
+use ruff_python_ast::{AnyNodeRef, NodeKind, PySourceType};
 use ruff_python_trivia::{
     is_pragma_comment, lines_after, lines_after_ignoring_trivia, lines_before, CommentLinePosition,
 };
@@ -13,11 +13,11 @@ use crate::prelude::*;
 use crate::statement::suite::should_insert_blank_line_after_class_in_stub_file;
 
 /// Formats the leading comments of a node.
-pub(crate) fn leading_node_comments<T>(node: &T) -> FormatLeadingComments
+pub(crate) fn leading_node_comments<'a, T>(node: T) -> FormatLeadingComments<'a>
 where
-    T: AstNode,
+    T: Into<AnyNodeRef<'a>>,
 {
-    FormatLeadingComments::Node(node.as_any_node_ref())
+    FormatLeadingComments::Node(node.into())
 }
 
 /// Formats the passed comments as leading comments
@@ -192,11 +192,11 @@ impl Format<PyFormatContext<'_>> for FormatTrailingComments<'_> {
 }
 
 /// Formats the dangling comments of `node`.
-pub(crate) fn dangling_node_comments<T>(node: &T) -> FormatDanglingComments
+pub(crate) fn dangling_node_comments<'a, T>(node: T) -> FormatDanglingComments<'a>
 where
-    T: AstNode,
+    T: Into<AnyNodeRef<'a>>,
 {
-    FormatDanglingComments::Node(node.as_any_node_ref())
+    FormatDanglingComments::Node(node.into())
 }
 
 pub(crate) fn dangling_comments(comments: &[SourceComment]) -> FormatDanglingComments {