Refactor diagnostic start|end location helpers (#20309)

- Renames functions to drop `expect_` from names.
- Make functions return `Option<LineColumn>` to appropriately signal
  when range is not available.
- Update existing consumers to use `unwrap_or_default()`. Uncertain if
  there are better fallback behaviors for individual consumers.

crates/ruff_linter/src/message/github.rs

@@ -19,7 +19,7 @@ impl Emitter for GithubEmitter {
         context: &EmitterContext,
     ) -> anyhow::Result<()> {
         for diagnostic in diagnostics {
-            let source_location = diagnostic.expect_ruff_start_location();
+            let source_location = diagnostic.ruff_start_location().unwrap_or_default();
             let filename = diagnostic.expect_ruff_filename();
             let location = if context.is_notebook(&filename) {
                 // We can't give a reasonable location for the structured formats,
@@ -29,7 +29,7 @@ impl Emitter for GithubEmitter {
                 source_location
             };
 
-            let end_location = diagnostic.expect_ruff_end_location();
+            let end_location = diagnostic.ruff_end_location().unwrap_or_default();
 
             write!(
                 writer,

crates/ruff_linter/src/message/grouped.rs

@@ -105,7 +105,7 @@ fn group_diagnostics_by_filename(
             .or_insert_with(Vec::new)
             .push(MessageWithLocation {
                 message: diagnostic,
-                start_location: diagnostic.expect_ruff_start_location(),
+                start_location: diagnostic.ruff_start_location().unwrap_or_default(),
             });
     }
     grouped_messages

crates/ruff_linter/src/message/sarif.rs

@@ -158,8 +158,8 @@ struct SarifResult<'a> {
 impl<'a> SarifResult<'a> {
     #[cfg(not(target_arch = "wasm32"))]
     fn from_message(message: &'a Diagnostic) -> Result<Self> {
-        let start_location = message.expect_ruff_start_location();
-        let end_location = message.expect_ruff_end_location();
+        let start_location = message.ruff_start_location().unwrap_or_default();
+        let end_location = message.ruff_end_location().unwrap_or_default();
         let path = normalize_path(&*message.expect_ruff_filename());
         Ok(Self {
             code: RuleCode::from(message),
@@ -178,8 +178,8 @@ impl<'a> SarifResult<'a> {
     #[cfg(target_arch = "wasm32")]
     #[expect(clippy::unnecessary_wraps)]
     fn from_message(message: &'a Diagnostic) -> Result<Self> {
-        let start_location = message.expect_ruff_start_location();
-        let end_location = message.expect_ruff_end_location();
+        let start_location = message.ruff_start_location().unwrap_or_default();
+        let end_location = message.ruff_end_location().unwrap_or_default();
         let path = normalize_path(&*message.expect_ruff_filename());
         Ok(Self {
             code: RuleCode::from(message),