feat: 增加关闭最后三个未驻留应用到任务栏上图标不消失的功能

增加最近打开区域的配置，在关闭未驻留应用的时候判断是否需要移除图标，同时更新配置

Log: 完成最近打开应用的功能
Influence: 任务栏-打开多个未驻留应用，然后依次关闭，当剩下最后三个的时候，观察是否还在任务栏
Bug: https://pms.uniontech.com/bug-view-147721.html
Change-Id: Ia78e973b41acb3e87c515f3bd8479f603b3dcdfd

misc/dconf/com.deepin.dde.dock.json

@@ -141,6 +141,16 @@
 			"description": "The dock gets different display mode, for instance, dock looks like win7 taskbar on classic mode.",
 			"permissions": "readwrite",
 			"visibility": "private"
+		},
+		"Recent_App": {
+			"value": [],
+			"serial": 0,
+			"flags": [],
+			"name": "Recent_App",
+			"name[zh_CN]": "*****",
+			"description": "The apps which has been opened recently when dock is started",
+			"permissions": "readwrite",
+			"visibility": "private"
 		}
 	}
 }