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

templates/devtest/devtest-list.tmpl

@@ -0,0 +1,13 @@
+{{template "devtest/devtest-header"}}
+<ul>
+	{{range .SubNames}}
+	<li><a href="{{AppSubUrl}}/devtest/{{.}}">{{.}}</a></li>
+	{{end}}
+</ul>
+
+<style>
+ul {
+	line-height: 2em;
+}
+</style>
+{{template "devtest/devtest-footer"}}