[MM-12667] Allow including deactivated users in bulk import and export (#10353)

* [MM-12667] Allow including deactivated users in bulk import and export

1. Added `deleteAt` for user type import line
2. Adding deactivated users data in bulk export
3. Importing deactivated users data in bulk import

Added/Updated relevant test cases

* Fixed export of replies to posts by deleted users.
Updated tests for same

app/export_converters.go

@@ -68,6 +68,7 @@ func ImportLineFromUser(user *model.User, exportedPrefs map[string]*string) *Lin
 			ChannelDisplayMode: exportedPrefs["ChannelDisplayMode"],
 			TutorialStep:       exportedPrefs["TutorialStep"],
 			EmailInterval:      exportedPrefs["EmailInterval"],
+			DeleteAt:           &user.DeleteAt,
 		},
 	}
 }