Add Quick start section for learn gitlab redesign

What does this MR do and why?

This merge request adds a new "Quick start" feature to Get started, creating a guided onboarding experience for users. The implementation includes a UI with expandable sections showing various tasks users can complete to get familiar with GitLab's workflow. Tasks are organized into categories like "Set up your code," "Configure a project," "Plan and execute work," and "Secure your deployment," with visual indicators showing completion status. The UI also includes a progress bar tracking overall completion.

The code adds policy rules to control who can invite members to a project based on membership lock settings, and introduces a presenter class to organize and display the onboarding tasks. Each task has attributes like title, tracking label, URL, and completion status, with some tasks being disabled if the user lacks sufficient permissions. The interface also highlights features available in GitLab Ultimate trial, encouraging users to try ultimate features.

Specifics/notes:

• changes are behind a feature flag

• handles basic page structure for use in further work items in https://gitlab.com/gitlab-org/gitlab/-/issues/537653

• add percentage bar

• add sections with actions and basic functionality per designs. See design discussions in https://gitlab.com/gitlab-org/gitlab/-/issues/538219

• a lot of core functionality is mimicked and improved upon at times from ee/app/assets/javascripts/pages/projects/learn_gitlab/components/learn_gitlab.vue

• items not handled in this MR, but will be in subsequent:

  • invite completion update task completed status and percentage w/o page refresh as done in learn gitlab
  • free version of page

• see https://gitlab.com/gitlab-org/gitlab/-/issues/537653 and more specifically https://gitlab.com/gitlab-org/gitlab/-/issues/538219

Screenshots or screen recordings

Click to expand

item	design discussion link	display
overall	https://gitlab.com/gitlab-org/gitlab/-/issues/538219#note_2484016807
general non privileged	https://gitlab.com/gitlab-org/gitlab/-/issues/538219#note_2484190894
general privileged	https://gitlab.com/gitlab-org/gitlab/-/issues/538219#note_2484190894
section: code	https://gitlab.com/gitlab-org/gitlab/-/issues/538219#note_2484050626
section: project	https://gitlab.com/gitlab-org/gitlab/-/issues/538219#note_2484084501	https://gitlab.com/-/project/278964/uploads/e169a4b1ac76c6374bfe5a4d8a181484/Screenshot_2025-05-05_at_1.06.58_PM.png
section: plan	https://gitlab.com/gitlab-org/gitlab/-/issues/538219#note_2484168930
section: secure	https://gitlab.com/gitlab-org/gitlab/-/issues/538219#note_2484176061
mobile	https://gitlab.com/gitlab-org/gitlab/-/issues/538219
privileged functional	https://gitlab.com/gitlab-org/gitlab/-/issues/538219	Screen_Recording_2025-05-06_at_9.04.07_AM
non privileged function	https://gitlab.com/gitlab-org/gitlab/-/issues/538219#note_2484190894	Screen_Recording_2025-05-06_at_9.06.00_AM
invite	https://gitlab.com/gitlab-org/gitlab/-/issues/538219#note_2484084501	Screen_Recording_2025-05-06_at_9.10.04_AM

How to set up and validate locally

Note: This is covered by feature spec in this MR and jest as much as possible.

Click to expand

1. Setup gdk to simulate SaaS - https://docs.gitlab.com/ee/development/ee_features.html#simulate-a-saas-instance and restart GDK
2. In rails console enable the feature flag

   Feature.enable(:learn_gitlab_redesign)

3. Create a new group and project.
4. In rails console, onboard that group that was just created

   ::Onboarding::Progress.onboard(Group.last)

5. In the gitlab admin UI, edit the group to be on an ultimate trial plan(edit button from http://gdk.test:3000/admin/groups)
6. In rails console(bundle exec rails c), change the trial, trial start and end date for the group

   Group.last.gitlab_subscription.update_columns(trial_starts_on: Date.today, trial_ends_on: 30.days.from_now, trial: true)

7. Go to the get started path for the group/project: For instance, http://gdk.test:3000/logan225-group/logan225-project/-/get_started

MR acceptance checklist

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

Related to #537653