Add domain verification operation views

Related issue #375492 (closed)

What does this MR do and why?

Add domain verification operation views.

The feature is under feature flag: domain_verification_operation

The haml views are copy from app/views/projects/pages_domains/. The main differences:

• Add a new project select component in create form
• UI changed(design link) and follow the new Pajamas design system
• Action link url changed
• Need add new documentation page replace the doc link

dependent MRs:

• !116641 (merged)
• !116626 (merged)

design link Figma

/cc @daveliu @qk44077907

Screenshots or screen recordings

Empty index page	Index page with domains

New domain page

Edit domain page

How to set up and validate locally

1. simulate the SaaS locally:

   export GITLAB_SIMULATE_SAAS=1

2. Upload Premium license to enable domain_verification feature

3. Enable pages in gitlab.yml:

   pages:
     enabled: true
     access_control: false
     host: example.com
     port: 80
     external_http: true
     external_https: true

4. enable domain_verification_operation feature in console:

   Feature.enable(:domain_verification_operation)

5. Change application settings in rails console:

   ApplicationSetting.current.update(pages_domain_verification_enabled: true, lets_encrypt_terms_of_service_accepted: true, 
   lets_encrypt_notification_email: "test@gitlab.com")

6. Visit domain verification page http://localhost:3000/groups/flightjs/-/settings/domain_verification

7. Click the Add Domain button.

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.