Introduce AutoindentMode parameter to Buffer::edit

This controls whether or not we preserve the relative indentation
of inserted text blocks.

Co-authored-by: Mikayla Maki <mikayla.c.maki@gmail.com>

crates/editor/src/display_map.rs

@@ -897,7 +897,7 @@ pub mod tests {
 
         let ix = snapshot.buffer_snapshot.text().find("seven").unwrap();
         buffer.update(cx, |buffer, cx| {
-            buffer.edit([(ix..ix, "and ")], cx);
+            buffer.edit([(ix..ix, "and ")], None, cx);
         });
 
         let snapshot = map.update(cx, |map, cx| map.snapshot(cx));
@@ -936,6 +936,7 @@ pub mod tests {
                     (Point::new(1, 1)..Point::new(1, 1), "\t"),
                     (Point::new(2, 1)..Point::new(2, 1), "\t"),
                 ],
+                None,
                 cx,
             )
         });