Stage only tracked files when staging all in filter-by-tracked-files view

Also, fix two other commands that stage all files under the hood:
- when continuing a rebase after resolving conflicts, we auto-stage all files,
  but in this case we never want to include untracked files, regardless of the
  filter
- likewise, pressing ctrl-f to find a base commit for fixup stages all files for
  convenience, but again, this should only stage files that are already tracked

pkg/integration/tests/filter_and_search/stage_all_stages_only_tracked_files_in_tracked_only_filter.go

@@ -48,10 +48,7 @@ var StageAllStagesOnlyTrackedFilesInTrackedOnlyFilter = NewIntegrationTest(NewIn
 			Lines(
 				Equals("▼ /").IsSelected(),
 				Equals("  M  file-tracked"), // 'M' is now in the left column, so file is staged
-				/* EXPECTED:
 				Equals("  ?? file-untracked"),
-				ACTUAL: */
-				Equals("  A  file-untracked"),
 			)
 	},
 })