Add metadata for Manage:Analytics docs

doc/user/analytics/code_review_analytics.md

 ---
 description: "Learn how long your open merge requests have spent in code review, and what distinguishes the longest-running." # Up to ~200 chars long. They will be displayed in Google Search snippets. It may help to write the page intro first, and then reuse it here.
+stage: Manage
+group: Analytics
+To determine the technical writer assigned to the Stage/Group associated with this page, see:
+  https://about.gitlab.com/handbook/engineering/ux/technical-writing/#designated-technical-writers
 ---
 
+
 # Code Review Analytics **(STARTER)**
 
 > [Introduced](https://gitlab.com/gitlab-org/gitlab/issues/38062) in [GitLab Starter](https://about.gitlab.com/pricing/) 12.7.

doc/user/analytics/index.md

+---
+stage: Manage
+group: Analytics
+To determine the technical writer assigned to the Stage/Group associated with this page, see:
+  https://about.gitlab.com/handbook/engineering/ux/technical-writing/#designated-technical-writers
+---
+
 # Analytics
 
 ## Analytics workspace

doc/user/analytics/productivity_analytics.md

+---
+stage: Manage
+group: Analytics
+To determine the technical writer assigned to the Stage/Group associated with this page, see:
+  https://about.gitlab.com/handbook/engineering/ux/technical-writing/#designated-technical-writers
+---
+
 # Productivity Analytics **(PREMIUM)**
 
 > [Introduced](https://gitlab.com/gitlab-org/gitlab/issues/12079) in [GitLab Premium](https://about.gitlab.com/pricing/) 12.3.

doc/user/analytics/value_stream_analytics.md

+---
+stage: Manage
+group: Analytics
+To determine the technical writer assigned to the Stage/Group associated with this page, see:
+  https://about.gitlab.com/handbook/engineering/ux/technical-writing/#designated-technical-writers
+---
+
 # Value Stream Analytics
 
 > - Introduced as Cycle Analytics prior to GitLab 12.3 at the project level.

doc/user/group/contribution_analytics/index.md

 ---
 type: reference
+stage: Manage
+group: Analytics
+To determine the technical writer assigned to the Stage/Group associated with this page, see:
+  https://about.gitlab.com/handbook/engineering/ux/technical-writing/#designated-technical-writers
 ---
-
 # Contribution Analytics **(STARTER)**
 
 > - Introduced in [GitLab Starter](https://about.gitlab.com/pricing/) 8.3.

doc/user/group/insights/index.md

 ---
 type: reference, howto
+stage: Manage
+group: Analytics
+To determine the technical writer assigned to the Stage/Group associated with this page, see:
+  https://about.gitlab.com/handbook/engineering/ux/technical-writing/#designated-technical-writers
 ---
 
 # Insights **(ULTIMATE)**

doc/user/group/issues_analytics/index.md

 ---
 type: reference
+stage: Manage
+group: Analytics
+To determine the technical writer assigned to the Stage/Group associated with this page, see:
+  https://about.gitlab.com/handbook/engineering/ux/technical-writing/#designated-technical-writers
 ---
 
 # Issues Analytics **(PREMIUM)**