Migrate deprecated bs-callout to alert component in pages

What does this MR do and why?

Migrate deprecated bs-callout to Pajamas::AlertComponent in app/views/projects/pages/*

It's a part of Pajamas adoption project

Changed according to migration guide available in next epic: &5213 (closed)

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

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Before	After

How to set up and validate locally

1. Enable external_http for gitlab pages in config/gitlab.yml:

development:
  pages:
    enabled: true
    access_control: false
    host: 127.0.0.1.nip.io
    port: 3010
    https: false # Set to true if you serve the pages with HTTPS
    external_http: ["1.1.1.1:80", "[2001::1]:80"] # If defined, enables custom domain support in GitLab Pages

2. Open some project
3. Goto Deploy -> Pages
4. Setup pages(if required).
5. Add new domain.
6. Verify warning messages. You can mock next methods to see warnings:

app/presenters/pages_domain_presenter.rb#L6

app/presenters/pages_domain_presenter.rb#L10

7. Modify account namespace name (to include dot .) to see the HTTPS with subdomains of subdomains warning message.

8. Disable pages for this project or mock it here app/models/project.rb#L2123 to see the pages are disabled warning message.

Related to #441112 (closed)

app/views/projects/pages/_ssl_limitations_warning.html.haml

-.bs-callout.bs-callout-warning
-  = sprite_icon("warning-solid", css_class: "gl-text-orange-600")
-  %strong= _("Warning:")
-  - pages_host = Gitlab.config.pages.host
-  - docs_link_start = "<a href='#{help_page_path('user/project/pages/introduction', anchor: 'subdomains-of-subdomains')}' target='_blank' rel='noopener noreferrer'>".html_safe
-  - link_end = '</a>'.html_safe
-  = s_("GitLabPages|When using Pages under the general domain of a GitLab instance (%{pages_host}), you cannot use HTTPS with subdomains of subdomains. If your namespace or groupname contains a dot, it does not work. This is a limitation of the HTTP Over TLS protocol. HTTP pages work if you don't redirect HTTP to HTTPS. %{docs_link_start}Learn more.%{link_end}").html_safe % { pages_host: pages_host, docs_link_start: docs_link_start, link_end: link_end }
+= render Pajamas::AlertComponent.new(dismissible: false,
+  alert_options: { class: 'gl-mb-5' },
+  variant: :warning) do |c|
+  - c.with_body do
+    %strong= _("Warning:")
+    - pages_host = Gitlab.config.pages.host
+    - docs_link_start = "<a href='#{help_page_path('user/project/pages/introduction', anchor: 'subdomains-of-subdomains')}' target='_blank' rel='noopener noreferrer'>".html_safe
+    - link_end = '</a>'.html_safe
+    = s_("GitLabPages|When using Pages under the general domain of a GitLab instance (%{pages_host}), you cannot use HTTPS with subdomains of subdomains. If your namespace or groupname contains a dot, it does not work. This is a limitation of the HTTP Over TLS protocol. HTTP pages work if you don't redirect HTTP to HTTPS. %{docs_link_start}Learn more.%{link_end}").html_safe % { pages_host: pages_host, docs_link_start: docs_link_start, link_end: link_end }