snippets: Preserve leading whitespace (#31933)

Closes #18481

Release Notes:

- Snippet insertions now preserve leading whitespace instead of using
language-specific auto-indentation.

crates/editor/src/editor.rs

@@ -8929,7 +8929,10 @@ impl Editor {
                 .iter()
                 .cloned()
                 .map(|range| (range, snippet_text.clone()));
-            buffer.edit(edits, Some(AutoindentMode::EachLine), cx);
+            let autoindent_mode = AutoindentMode::Block {
+                original_indent_columns: Vec::new(),
+            };
+            buffer.edit(edits, Some(autoindent_mode), cx);
 
             let snapshot = &*buffer.read(cx);
             let snippet = &snippet;