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">

lib/discourse_dev/email_log.rb

@@ -0,0 +1,77 @@
+# frozen_string_literal: true
+
+require "discourse_dev/record"
+require "faker"
+
+module DiscourseDev
+  class EmailLog < Record
+    def initialize
+      super(::EmailLog, DiscourseDev.config.email_logs[:count])
+    end
+
+    def create_sent!
+      ::EmailLog.create!(email_log_data)
+    end
+
+    def create_bounced!
+      bounce_key = SecureRandom.hex
+      email_local_part, email_domain = SiteSetting.notification_email.split("@")
+      bounced_to_address = "#{email_local_part}+verp-#{bounce_key}@#{email_domain}"
+      bounce_data =
+        email_log_data.merge(
+          to_address: bounced_to_address,
+          bounced: true,
+          bounce_key: bounce_key,
+          bounce_error_code: "5.0.0",
+        )
+
+      # Bounced email logs require a matching incoming email record
+      ::IncomingEmail.create!(
+        incoming_email_data.merge(to_addresses: bounced_to_address, is_bounce: true),
+      )
+      ::EmailLog.create!(bounce_data)
+    end
+
+    def create_rejected!
+      ::IncomingEmail.create!(incoming_email_data)
+    end
+
+    def email_log_data
+      {
+        to_address: User.random.email,
+        email_type: :digest,
+        user_id: User.random.id,
+        raw: Faker::Lorem.paragraph,
+      }
+    end
+
+    def incoming_email_data
+      user = User.random
+      subject = Faker::Lorem.sentence
+      email_content = <<-EMAIL
+        Return-Path: #{user.email}
+        From: #{user.email}
+        Date: #{Date.today}
+        Mime-Version: "1.0"
+        Content-Type: "text/plain"
+        Content-Transfer-Encoding: "7bit"
+
+        #{Faker::Lorem.paragraph}
+      EMAIL
+
+      {
+        user_id: user.id,
+        from_address: user.email,
+        raw: email_content,
+        error: Faker::Lorem.sentence,
+        rejection_message: I18n.t("emails.incoming.errors.bounced_email_error"),
+      }
+    end
+
+    def populate!
+      @count.times { create_sent! }
+      @count.times { create_bounced! }
+      @count.times { create_rejected! }
+    end
+  end
+end