Removing trailing whitespace inside multiline strings is unsafe (#9744)

Fix #8037.

crates/ruff_python_index/src/multiline_ranges.rs

@@ -0,0 +1,46 @@
+use ruff_python_parser::Tok;
+use ruff_text_size::TextRange;
+
+/// Stores the range of all multiline strings in a file sorted by
+/// [`TextRange::start`].
+pub struct MultilineRanges {
+    ranges: Vec<TextRange>,
+}
+
+impl MultilineRanges {
+    /// Returns `true` if the given range is inside a multiline string.
+    pub fn intersects(&self, target: TextRange) -> bool {
+        self.ranges
+            .binary_search_by(|range| {
+                if range.contains_range(target) {
+                    std::cmp::Ordering::Equal
+                } else if range.end() < target.start() {
+                    std::cmp::Ordering::Less
+                } else {
+                    std::cmp::Ordering::Greater
+                }
+            })
+            .is_ok()
+    }
+}
+
+#[derive(Default)]
+pub(crate) struct MultilineRangesBuilder {
+    ranges: Vec<TextRange>,
+}
+
+impl MultilineRangesBuilder {
+    pub(crate) fn visit_token(&mut self, token: &Tok, range: TextRange) {
+        if let Tok::String { triple_quoted, .. } = token {
+            if *triple_quoted {
+                self.ranges.push(range);
+            }
+        }
+    }
+
+    pub(crate) fn finish(self) -> MultilineRanges {
+        MultilineRanges {
+            ranges: self.ranges,
+        }
+    }
+}