refactor(i18n): 扁平化所有国际化语言文件的翻译结构

移除多层嵌套的翻译对象，将所有翻译项直接挂载到顶层lang对象上，统一代码结构

lang/en-us/fenxiao/bill.js

@@ -1,16 +1,10 @@
 export const lang = {
 	//title为每个页面的标题
 	title: 'Bill',
-	// fenxiao/bill.vue page new translation items
-	fenxiao: {
-		// Bill
-		bill: {
-			// Bill number prefix
-			billNoPrefix: 'Bill No.:',
-			// No bill information
-			noBill: 'No bill information',
-			// Distribution is not enabled by merchant
-			addonClosed: 'Distribution is not enabled by merchant',
-		},
-	},
+	// Bill number prefix
+	billNoPrefix: 'Bill No.:',
+	// No bill information
+	noBill: 'No bill information',
+	// Distribution is not enabled by merchant
+	addonClosed: 'Distribution is not enabled by merchant',
 }