Consolidate DORA docs

What does this MR do and why?

Originally, DORA metrics were introduced as part of CI/CD analytics and only later we added the APIs the tiles to VSA and Insights. As a result, DORA capabilities are now spread across multiple platform pages. Following the new category for DORA, we need to consolidate our DORA docs in one page.

This related to Add new DORA Metrics category (gitlab-com/www-gitlab-com!111590 - merged)

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doc/user/analytics/ci_cd_analytics.md

@@ -6,7 +6,7 @@ info: To determine the technical writer assigned to the Stage/Group associated w
 
 # CI/CD analytics **(FREE)**
 
-Use the CI/CD analytics page to view pipeline success rates and duration, and the history of [DORA metrics](index.md#devops-research-and-assessment-dora-key-metrics) over time.
+Use the CI/CD analytics page to view pipeline success rates and duration, and the history of DORA metrics over time.
 
 ## Pipeline success and duration charts
 
@@ -44,7 +44,7 @@ frequency to the `production` environment. The environment must be part of the
 [production deployment tier](../../ci/environments/index.md#deployment-tier-of-environments)
 for its deployment information to appear on the graphs.
 
-  Deployment frequency is one of the four [DORA metrics](index.md#devops-research-and-assessment-dora-key-metrics) that DevOps teams use for measuring excellence in software delivery.
+  Deployment frequency is one of the four DORA metrics that DevOps teams use for measuring excellence in software delivery.
 
 The deployment frequency chart is available for groups and projects.
 
@@ -68,7 +68,7 @@ merge requests to be deployed to a production environment. This chart is availab
 - For time periods in which no merge requests were deployed, the charts render a
   red, dashed line.
 
-  Lead time for changes is one of the four [DORA metrics](index.md#devops-research-and-assessment-dora-key-metrics) that DevOps teams use for measuring excellence in software delivery.
+  Lead time for changes is one of the four DORA metrics that DevOps teams use for measuring excellence in software delivery.
 
 To view the lead time for changes chart:
 
@@ -84,7 +84,7 @@ To view the lead time for changes chart:
 
 The time to restore service chart shows information about the median time an incident was open in a production environment. This chart is available for groups and projects.
 
-Time to restore service is one of the four [DORA metrics](index.md#devops-research-and-assessment-dora-key-metrics) that DevOps teams use for measuring excellence in software delivery.
+Time to restore service is one of the four DORA metrics that DevOps teams use for measuring excellence in software delivery.
 
 To view the time to restore service chart:
 
@@ -100,7 +100,7 @@ To view the time to restore service chart:
 
 The change failure rate chart shows information about the percentage of deployments that cause an incident in a production environment. This chart is available for groups and projects.
 
-Change failure rate is one of the four [DORA metrics](index.md#devops-research-and-assessment-dora-key-metrics) that DevOps teams use for measuring excellence in software delivery.
+Change failure rate is one of the four DORA metrics that DevOps teams use for measuring excellence in software delivery.
 
 To view the change failure rate chart: