Add busy count for integration tests

Integration tests need to be notified when Lazygit is idle so they can progress to the next assertion / user action.

pkg/integration/tests/interactive_rebase/squash_fixups_above_first_commit.go

@@ -30,7 +30,7 @@ var SquashFixupsAboveFirstCommit = NewIntegrationTest(NewIntegrationTestArgs{
 					Content(Contains("Are you sure you want to create a fixup! commit for commit")).
 					Confirm()
 			}).
-			NavigateToLine(Contains("commit 01")).
+			NavigateToLine(Contains("commit 01").DoesNotContain("fixup!")).
 			Press(keys.Commits.SquashAboveCommits).
 			Tap(func() {
 				t.ExpectPopup().Confirmation().