Remove exception-handler lexing from unused-bound-exception fix (#5851)

## Summary

The motivation here is that it will make this rule easier to rewrite as
a deferred check. Right now, we can't run this rule in the deferred
phase, because it depends on the `except_handler` to power its autofix.
Instead of lexing the `except_handler`, we can use the `SimpleTokenizer`
from the formatter, and just lex forwards and backwards.

For context, this rule detects the unused `e` in:

```python
try:
  pass
except ValueError as e:
  pass
```

crates/ruff_python_formatter/src/statement/stmt_class_def.rs

@@ -1,12 +1,13 @@
-use crate::comments::trailing_comments;
-
-use crate::expression::parentheses::{parenthesized, Parentheses};
-use crate::prelude::*;
-use crate::trivia::{SimpleTokenizer, TokenKind};
-use ruff_formatter::write;
 use ruff_text_size::TextRange;
 use rustpython_parser::ast::{Ranged, StmtClassDef};
 
+use ruff_formatter::write;
+use ruff_python_whitespace::{SimpleTokenizer, TokenKind};
+
+use crate::comments::trailing_comments;
+use crate::expression::parentheses::{parenthesized, Parentheses};
+use crate::prelude::*;
+
 #[derive(Default)]
 pub struct FormatStmtClassDef;
 

crates/ruff_python_formatter/src/statement/stmt_function_def.rs

@@ -2,12 +2,12 @@ use rustpython_parser::ast::{Ranged, StmtFunctionDef};
 
 use ruff_formatter::{write, FormatOwnedWithRule, FormatRefWithRule};
 use ruff_python_ast::function::AnyFunctionDefinition;
+use ruff_python_whitespace::{lines_after, skip_trailing_trivia};
 
 use crate::comments::{leading_comments, trailing_comments};
 use crate::context::NodeLevel;
 use crate::expression::parentheses::{optional_parentheses, Parentheses};
 use crate::prelude::*;
-use crate::trivia::{lines_after, skip_trailing_trivia};
 use crate::FormatNodeRule;
 
 #[derive(Default)]

crates/ruff_python_formatter/src/statement/stmt_with.rs

@@ -3,13 +3,13 @@ use rustpython_parser::ast::{Ranged, StmtAsyncWith, StmtWith, Suite, WithItem};
 
 use ruff_formatter::{format_args, write, FormatError};
 use ruff_python_ast::node::AnyNodeRef;
+use ruff_python_whitespace::{SimpleTokenizer, TokenKind};
 
 use crate::comments::trailing_comments;
 use crate::expression::parentheses::{
     in_parentheses_only_soft_line_break_or_space, optional_parentheses,
 };
 use crate::prelude::*;
-use crate::trivia::{SimpleTokenizer, TokenKind};
 use crate::FormatNodeRule;
 
 pub(super) enum AnyStatementWith<'a> {

crates/ruff_python_formatter/src/statement/suite.rs

@@ -1,10 +1,12 @@
-use crate::context::NodeLevel;
-use crate::prelude::*;
-use crate::trivia::lines_before;
+use rustpython_parser::ast::{Ranged, Stmt, Suite};
+
 use ruff_formatter::{
     format_args, write, FormatOwnedWithRule, FormatRefWithRule, FormatRuleWithOptions,
 };
-use rustpython_parser::ast::{Ranged, Stmt, Suite};
+use ruff_python_whitespace::lines_before;
+
+use crate::context::NodeLevel;
+use crate::prelude::*;
 
 /// Level at which the [`Suite`] appears in the source code.
 #[derive(Copy, Clone, Debug)]
@@ -185,13 +187,15 @@ impl<'ast> IntoFormat<PyFormatContext<'ast>> for Suite {
 
 #[cfg(test)]
 mod tests {
+    use rustpython_parser::ast::Suite;
+    use rustpython_parser::Parse;
+
+    use ruff_formatter::format;
+
     use crate::comments::Comments;
     use crate::prelude::*;
     use crate::statement::suite::SuiteLevel;
     use crate::PyFormatOptions;
-    use ruff_formatter::format;
-    use rustpython_parser::ast::Suite;
-    use rustpython_parser::Parse;
 
     fn format_suite(level: SuiteLevel) -> String {
         let source = r#"