API Catalog -> Service Catalog Migration

[brett0000FF]

What does this PR do? What is the motivation?

Integrate API Catalog docs into Service Catalog to reflect the new state of the product.

To do

• Fix broken links and update content in linked Admin Guide and Metrics docs.
• [ ]

Merge instructions

Merge readiness:

• Ready for merge

Merge queue is enabled in this repo. To have it automatically merged after it receives the required reviews, create the PR (from a branch that follows the <yourname>/description naming convention) and then add the following PR comment:

/merge

Additional notes

[github-actions]

Preview links (active after the build_preview check completes)

Removed or renamed files (these should redirect)

• https://docs-staging.datadoghq.com/brett.blue/DOCS-9666/api_catalog/troubleshoot

Renamed files

• https://docs-staging.datadoghq.com/brett.blue/DOCS-9666/service_catalog/api_catalog/
• https://docs-staging.datadoghq.com/brett.blue/DOCS-9666/service_catalog/api_catalog/add_entries
• https://docs-staging.datadoghq.com/brett.blue/DOCS-9666/service_catalog/api_catalog/add_metadata
• https://docs-staging.datadoghq.com/brett.blue/DOCS-9666/service_catalog/api_catalog/api_catalog_api
• https://docs-staging.datadoghq.com/brett.blue/DOCS-9666/service_catalog/api_catalog/discover_endpoints
• https://docs-staging.datadoghq.com/brett.blue/DOCS-9666/service_catalog/api_catalog/explore_endpoints
• https://docs-staging.datadoghq.com/brett.blue/DOCS-9666/service_catalog/api_catalog/monitor_endpoints
• https://docs-staging.datadoghq.com/brett.blue/DOCS-9666/service_catalog/api_catalog/owners_and_tags

Modified Files

• https://docs-staging.datadoghq.com/brett.blue/DOCS-9666/service_catalog/customize/
• https://docs-staging.datadoghq.com/brett.blue/DOCS-9666/service_catalog/manage
• https://docs-staging.datadoghq.com/brett.blue/DOCS-9666/service_catalog/troubleshooting