Refactor some frontend problems (#32646)

1. correct the modal usage on "admin email list" page (then
`web_src/js/features/admin/emails.ts` is removed)
2. use `addDelegatedEventListener` instead of `jQuery().on`
3. more jQuery related changes and remove jQuery from
`web_src/js/features/common-button.ts`
4. improve `confirmModal` to make it support header, and remove
incorrect double-escaping
5. fix more typescript related types
6. fine tune devtest pages and add more tests

routers/web/devtest/devtest.go

@@ -24,12 +24,12 @@ func List(ctx *context.Context) {
 	var subNames []string
 	for _, tmplName := range templateNames {
 		subName := strings.TrimSuffix(tmplName, ".tmpl")
-		if subName != "list" {
+		if !strings.HasPrefix(subName, "devtest-") {
 			subNames = append(subNames, subName)
 		}
 	}
 	ctx.Data["SubNames"] = subNames
-	ctx.HTML(http.StatusOK, "devtest/list")
+	ctx.HTML(http.StatusOK, "devtest/devtest-list")
 }
 
 func FetchActionTest(ctx *context.Context) {