--show-settings displays active settings in a far more readable format (#9464)

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## Summary

Fixes #8334.

`Display` has been implemented for `ruff_workspace::Settings`, which
gives a much nicer and more readable output to `--show-settings`.

Internally, a `display_settings` utility macro has been implemented to
reduce the boilerplate of the display code.

### Work to be done

- [x] A lot of formatting for `Vec<_>` and `HashSet<_>` types have been
stubbed out, using `Debug` as a fallback. There should be a way to add
generic formatting support for these types as a modifier in
`display_settings`.
- [x] Several complex types were also stubbed out and need proper
`Display` implementations rather than falling back on `Debug`.
- [x] An open question needs to be answered: how important is it that
the output be valid TOML? Some types in settings, such as a hash-map
from a glob pattern to a multi-variant enum, will be hard to rework into
valid _and_ readable TOML.
- [x] Tests need to be implemented.

## Test Plan

Tests consist of a snapshot test for the default `--show-settings`
output and a doctest for `display_settings!`.

crates/ruff_python_formatter/src/options.rs

@@ -2,6 +2,7 @@ use ruff_formatter::printer::{LineEnding, PrinterOptions, SourceMapGeneration};
 use ruff_formatter::{FormatOptions, IndentStyle, IndentWidth, LineWidth};
 use ruff_macros::CacheKey;
 use ruff_python_ast::PySourceType;
+use std::fmt;
 use std::path::Path;
 use std::str::FromStr;
 
@@ -241,6 +242,16 @@ pub enum QuoteStyle {
     Preserve,
 }
 
+impl fmt::Display for QuoteStyle {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Single => write!(f, "single"),
+            Self::Double => write!(f, "double"),
+            Self::Preserve => write!(f, "preserve"),
+        }
+    }
+}
+
 impl FromStr for QuoteStyle {
     type Err = &'static str;
 
@@ -277,6 +288,15 @@ impl MagicTrailingComma {
     }
 }
 
+impl fmt::Display for MagicTrailingComma {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Respect => write!(f, "respect"),
+            Self::Ignore => write!(f, "ignore"),
+        }
+    }
+}
+
 impl FromStr for MagicTrailingComma {
     type Err = &'static str;
 
@@ -306,6 +326,15 @@ impl PreviewMode {
     }
 }
 
+impl fmt::Display for PreviewMode {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Disabled => write!(f, "disabled"),
+            Self::Enabled => write!(f, "enabled"),
+        }
+    }
+}
+
 #[derive(Copy, Clone, Debug, Eq, PartialEq, Default, CacheKey)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 #[cfg_attr(feature = "serde", serde(rename_all = "lowercase"))]
@@ -323,6 +352,15 @@ impl DocstringCode {
     }
 }
 
+impl fmt::Display for DocstringCode {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Disabled => write!(f, "disabled"),
+            Self::Enabled => write!(f, "enabled"),
+        }
+    }
+}
+
 #[derive(Copy, Clone, Default, Eq, PartialEq, CacheKey)]
 #[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 #[cfg_attr(feature = "serde", serde(rename_all = "lowercase"))]
@@ -338,8 +376,8 @@ pub enum DocstringCodeLineWidth {
     Dynamic,
 }
 
-impl std::fmt::Debug for DocstringCodeLineWidth {
-    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+impl fmt::Debug for DocstringCodeLineWidth {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match *self {
             DocstringCodeLineWidth::Fixed(v) => v.value().fmt(f),
             DocstringCodeLineWidth::Dynamic => "dynamic".fmt(f),
@@ -347,6 +385,15 @@ impl std::fmt::Debug for DocstringCodeLineWidth {
     }
 }
 
+impl fmt::Display for DocstringCodeLineWidth {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Fixed(width) => width.fmt(f),
+            Self::Dynamic => write!(f, "dynamic"),
+        }
+    }
+}
+
 /// Responsible for deserializing the `DocstringCodeLineWidth::Dynamic`
 /// variant.
 fn deserialize_docstring_code_line_width_dynamic<'de, D>(d: D) -> Result<(), D::Error>