DEV: Convert admin-incoming-email modal to component-based API (#22701)

- Convert `admin-incoming-email` modal to component-based API
- Testing that the modal was working in local development was extremely challenging due to the need for `rejected` and `bounced` emails. Something that is not easy to stub in a local dev environment. To make this process more smooth for future developers I have added a new rake task:

```
desc "Creates sample email logs"
task "email_logs:populate" => ["db:load_config"] do |_, args|
  DiscourseDev::EmailLog.populate!
end
```

That will generate fully functional email logs in development to be toyed with.

<img width="787" alt="Screenshot 2023-07-20 at 3 27 04 PM" src="https://github.com/discourse/discourse/assets/50783505/47b3fe34-cd7e-49a5-8fe6-768c0fbd1aa2">

app/assets/javascripts/admin/addon/controllers/modals/admin-incoming-email.js

@@ -1,28 +0,0 @@
-import Controller from "@ember/controller";
-import IncomingEmail from "admin/models/incoming-email";
-import ModalFunctionality from "discourse/mixins/modal-functionality";
-import discourseComputed from "discourse-common/utils/decorators";
-import { longDate } from "discourse/lib/formatter";
-import { popupAjaxError } from "discourse/lib/ajax-error";
-
-export default class AdminIncomingEmailController extends Controller.extend(
-  ModalFunctionality
-) {
-  @discourseComputed("model.date")
-  date(d) {
-    return longDate(d);
-  }
-
-  load(id) {
-    return IncomingEmail.find(id).then((result) => this.set("model", result));
-  }
-
-  loadFromBounced(id) {
-    return IncomingEmail.findByBounced(id)
-      .then((result) => this.set("model", result))
-      .catch((error) => {
-        this.send("closeModal");
-        popupAjaxError(error);
-      });
-  }
-}