Implement new Foundations product structure

Overview

⚠ The review app for this MR is broken. Please review the changes via https://jtucker-notifications-category-2.about.gitlab-review.app/direction/manage/.

This MR implements the structure agreed upon in https://gitlab.com/gitlab-com/Product/-/issues/13078+. Once merged, the Manage stage will have the following structure:

graph LR;
  s_manage["Stage: Manage"]-->g_foundations["Group: Foundations"];
  s_manage-->g_design["Group: Design System"];
  s_manage-->g_papercuts["Group: UX Paper cuts"];
  s_manage-->g_import["Group: Import & Integrate"];
  g_foundations-->c_nav["Category: Navigation"];
  g_foundations-->c_settings["Category: Settings"];
  g_foundations-->c_notifications["Category: Notifications"];
  g_foundations-->c_docs["Category: Docs site"];
  g_design-->c_design["Category: Pajamas"];
  g_import-->c_api["Category: API"];
  g_import-->c_integrations["Category: Integrations"];
  g_import-->c_webhooks["Category: Webhooks"];
  g_import-->c_importers["Category: Importers"];
  g_import-->c_i18n["Category: Internationalization"];

Note that this MR does not yet change any group or stage names, as that will require significant work across the organization. We will start that work in a follow-up MR.

Specific changes:

• Adds a new "Notifications" category that absorbs notifications and todos features from "Team planning" category
• Breaks the "Nav & Settings" category into two separate categories, each with their own direction page
• Convert the Design System category direction page into the Design System group direction page
• Move the UX Paper Cuts direction page into the Manage stage

Approvals

Merge requests with changes to stages and groups and significant changes to categories need to be created, approved, and/or merged by each of the below:

• Chief Product Officer @david (post MR link in chief-product-officer once all others have approved)
• PLT Leader relevant to the affected Section(s) @steve-evangelista OR @hbenson OR @mflouton OR @justinfarris
• The Product Director relevant to the affected Section(s)
• The Engineering Director relevant to the affected Section(s)
• Director of Product Design @vkarnes

Note: Chief Product Officer approval should be requested once all other approvals have been completed. To request approval, post the MR link in the #chief-product-officer channel tagging @david and cc'ing @Gena Schwam.

The following people need to be on the merge request so they stay informed:

• Chief Technology Officer @joergheilig
• Development Leader relevant to the affected Section(s) @timzallmann OR @bmarnane OR @meks
• VP of Infrastructure & Quality Engineering @meks
• VP of UX @david (Acting VP of UX leader)
• Director of Technical Writing @susantacker
• Engineering Productivity (by @ mentioning @gl-quality/eng-prod)
• The Product Marketing Manager relevant to the stage group(s)

After Approvals and Merge

• Create an issue in the gitlab-org/quality/triage-ops project to update GitLab Bot automation:
  • for Category change
  • for Stage or Group change
  • If label migration is required, please follow the self-serve instructions to get started on a one-off label migration MR
• Open an MR in the gitlab-org/gitlab project to update any reference of the previous group label to the new one
• Mention the product group Technical Writer to update the documentation metadata
• Share MR in #product, #development, and relevant #s_, #g_, and #f_ Slack channels