Implement Ranged on more structs (#6639)

## Summary

I noticed some inconsistencies around uses of `.range.start()`, structs
that have a `TextRange` field but don't implement `Ranged`, etc.

## Test Plan

`cargo test`

crates/ruff_python_ast/src/stmt_if.rs

@@ -24,6 +24,12 @@ pub struct IfElifBranch<'a> {
     pub range: TextRange,
 }
 
+impl Ranged for IfElifBranch<'_> {
+    fn range(&self) -> TextRange {
+        self.range
+    }
+}
+
 pub fn if_elif_branches(stmt_if: &StmtIf) -> impl Iterator<Item = IfElifBranch> {
     iter::once(IfElifBranch {
         kind: BranchKind::If,