Remove parentheses around multiple exception types on Python 3.14+ (#20768)

Summary
--

This PR implements the black preview style from
https://github.com/psf/black/pull/4720. As of Python 3.14, you're
allowed to omit the parentheses around groups of exceptions, as long as
there's no `as` binding:

**3.13**

```pycon
Python 3.13.4 (main, Jun  4 2025, 17:37:06) [Clang 20.1.4 ] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> try: ...
... except (Exception, BaseException): ...
...
Ellipsis
>>> try: ...
... except Exception, BaseException: ...
...
  File "<python-input-1>", line 2
    except Exception, BaseException: ...
           ^^^^^^^^^^^^^^^^^^^^^^^^
SyntaxError: multiple exception types must be parenthesized
```

**3.14**

```pycon
Python 3.14.0rc2 (main, Sep  2 2025, 14:20:56) [Clang 20.1.4 ] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> try: ...
... except Exception, BaseException: ...
...
Ellipsis
>>> try: ...
... except (Exception, BaseException): ...
...
Ellipsis
>>> try: ...
... except Exception, BaseException as e: ...
...
  File "<python-input-2>", line 2
    except Exception, BaseException as e: ...
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
SyntaxError: multiple exception types must be parenthesized when using 'as'
```

I think this ended up being pretty straightforward, at least once Micha
showed me where to start :)

Test Plan
--

New tests

At first I thought we were deviating from black in how we handle
comments within the exception type tuple, but I think this applies to
how we format all tuples, not specifically with the new preview style.

crates/ruff_python_formatter/src/cli.rs

@@ -6,7 +6,7 @@ use anyhow::{Context, Result};
 use clap::{Parser, ValueEnum, command};
 
 use ruff_formatter::SourceCode;
-use ruff_python_ast::PySourceType;
+use ruff_python_ast::{PySourceType, PythonVersion};
 use ruff_python_parser::{ParseOptions, parse};
 use ruff_python_trivia::CommentRanges;
 use ruff_text_size::Ranged;
@@ -42,13 +42,19 @@ pub struct Cli {
     pub print_comments: bool,
     #[clap(long, short = 'C')]
     pub skip_magic_trailing_comma: bool,
+    #[clap(long)]
+    pub target_version: PythonVersion,
 }
 
 pub fn format_and_debug_print(source: &str, cli: &Cli, source_path: &Path) -> Result<String> {
     let source_type = PySourceType::from(source_path);
 
     // Parse the AST.
-    let parsed = parse(source, ParseOptions::from(source_type)).context("Syntax error in input")?;
+    let parsed = parse(
+        source,
+        ParseOptions::from(source_type).with_target_version(cli.target_version),
+    )
+    .context("Syntax error in input")?;
 
     let options = PyFormatOptions::from_extension(source_path)
         .with_preview(if cli.preview {
@@ -60,7 +66,8 @@ pub fn format_and_debug_print(source: &str, cli: &Cli, source_path: &Path) -> Re
             MagicTrailingComma::Ignore
         } else {
             MagicTrailingComma::Respect
-        });
+        })
+        .with_target_version(cli.target_version);
 
     let source_code = SourceCode::new(source);
     let comment_ranges = CommentRanges::from(parsed.tokens());