editor: Trim indent guides at last non-empty line (#29482)

Closes #26274

Adjust the end position of indent guides to prevent them from extending
through empty space.
Also corrected old test values ​​that seemed to have adapted to the
indentation's behavior.

Release Notes:

- Fixed indentation guides extending beyond the final scope in a file.

crates/editor/src/editor_tests.rs

@@ -16520,7 +16520,7 @@ async fn test_indent_guide_tabs(cx: &mut TestAppContext) {
     assert_indent_guides(
         0..6,
         vec![
-            indent_guide(buffer_id, 1, 6, 0),
+            indent_guide(buffer_id, 1, 5, 0),
             indent_guide(buffer_id, 3, 4, 1),
         ],
         None,

crates/multi_buffer/src/multi_buffer.rs

@@ -5793,7 +5793,7 @@ impl MultiBufferSnapshot {
                 line_indent.len(tab_size) / tab_size
                     + ((line_indent.len(tab_size) % tab_size) > 0) as u32
             } else {
-                current_depth
+                0
             };
 
             match depth.cmp(&current_depth) {