Add tests for skip magic trailing comma

<!--
Thank you for contributing to Ruff! To help us out with reviewing, please consider the following:

- Does this pull request include a summary of the change? (See below.)
- Does this pull request include a descriptive title?
- Does this pull request include references to any relevant issues?
-->

## Summary

This PR adds tests that verify that the magic trailing comma is not respected if disabled in the formatter options. 

Our test setup now allows to create a `<fixture-name>.options.json` file that contains an array of configurations that should be tested. 

<!-- What's the purpose of the change? What does it do, and why? -->

## Test Plan

It's all about tests :) 

<!-- How was it tested? -->

crates/ruff_python_formatter/src/builders.rs

@@ -220,7 +220,7 @@ impl<'fmt, 'ast, 'buf> JoinCommaSeparatedBuilder<'fmt, 'ast, 'buf> {
         if let Some(last_end) = self.last_end.take() {
             if_group_breaks(&text(",")).fmt(self.fmt)?;
 
-            if self.fmt.options().magic_trailing_comma().is_preserve()
+            if self.fmt.options().magic_trailing_comma().is_respect()
                 && matches!(
                     first_non_trivia_token(last_end, self.fmt.context().contents()),
                     Some(Token {

crates/ruff_python_formatter/src/options.rs

@@ -2,6 +2,11 @@ use ruff_formatter::printer::{LineEnding, PrinterOptions};
 use ruff_formatter::{FormatOptions, IndentStyle, LineWidth};
 
 #[derive(Clone, Debug)]
+#[cfg_attr(
+    feature = "serde",
+    derive(serde::Serialize, serde::Deserialize),
+    serde(default)
+)]
 pub struct PyFormatOptions {
     /// Specifies the indent style:
     /// * Either a tab
@@ -9,6 +14,7 @@ pub struct PyFormatOptions {
     indent_style: IndentStyle,
 
     /// The preferred line width at which the formatter should wrap lines.
+    #[cfg_attr(feature = "serde", serde(default = "default_line_width"))]
     line_width: LineWidth,
 
     /// The preferred quote style to use (single vs double quotes).
@@ -18,6 +24,10 @@ pub struct PyFormatOptions {
     magic_trailing_comma: MagicTrailingComma,
 }
 
+fn default_line_width() -> LineWidth {
+    LineWidth::try_from(88).unwrap()
+}
+
 impl PyFormatOptions {
     pub fn magic_trailing_comma(&self) -> MagicTrailingComma {
         self.magic_trailing_comma
@@ -36,6 +46,16 @@ impl PyFormatOptions {
         self.magic_trailing_comma = trailing_comma;
         self
     }
+
+    pub fn with_indent_style(&mut self, indent_style: IndentStyle) -> &mut Self {
+        self.indent_style = indent_style;
+        self
+    }
+
+    pub fn with_line_width(&mut self, line_width: LineWidth) -> &mut Self {
+        self.line_width = line_width;
+        self
+    }
 }
 
 impl FormatOptions for PyFormatOptions {
@@ -69,6 +89,11 @@ impl Default for PyFormatOptions {
 }
 
 #[derive(Copy, Clone, Debug, Default, Eq, PartialEq)]
+#[cfg_attr(
+    feature = "serde",
+    derive(serde::Serialize, serde::Deserialize),
+    serde(rename_all = "kebab-case")
+)]
 pub enum QuoteStyle {
     Single,
     #[default]
@@ -105,14 +130,19 @@ impl TryFrom<char> for QuoteStyle {
 }
 
 #[derive(Copy, Clone, Debug, Default)]
+#[cfg_attr(
+    feature = "serde",
+    derive(serde::Serialize, serde::Deserialize),
+    serde(rename_all = "kebab-case")
+)]
 pub enum MagicTrailingComma {
     #[default]
-    Preserve,
-    Skip,
+    Respect,
+    Ignore,
 }
 
 impl MagicTrailingComma {
-    pub const fn is_preserve(self) -> bool {
-        matches!(self, Self::Preserve)
+    pub const fn is_respect(self) -> bool {
+        matches!(self, Self::Respect)
     }
 }