docs: move pages from federation

[Meschreiber]

This PR moves some pages that are currently in the federation repo but appear in the Routing section of our docs. This is a completion of the effort started here: https://github.com/apollographql/router/pull/6157

[svc-apollo-docs]

✅ Docs Preview Ready

Configuration

```json { "repoOverrides": { "apollographql/router@main": { "remote": { "owner": "apollographql", "repo": "router", "branch": "docs/move-pages-from-federation" } } } } ```

Name	Link
Commit	6849af4d32f4e1f10553b60706a365acb9c8cfcc
Preview	[https://www.apollographql.com/docs/deploy-preview/67cd1a0e2cd5d96c31c8](https://www.apollographql.com/docs/deploy-preview/67cd1a0e2cd5d96c31c8)
Build ID	67cd1a0e2cd5d96c31c8
File Changes	0 new, 1 changed, 0 removed ``` * graphos/routing/about-router.mdx ```
Pages	1

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1 pages published. Build will be available for 30 days.

[router-perf[bot]]

CI performance tests

• [ ] connectors-const - Connectors stress test that runs with a constant number of users
• [x] const - Basic stress test that runs with a constant number of users
• [ ] demand-control-instrumented - A copy of the step test, but with demand control monitoring and metrics enabled
• [ ] demand-control-uninstrumented - A copy of the step test, but with demand control monitoring enabled
• [ ] enhanced-signature - Enhanced signature enabled
• [ ] events - Stress test for events with a lot of users and deduplication ENABLED
• [ ] events_big_cap_high_rate - Stress test for events with a lot of users, deduplication enabled and high rate event with a big queue capacity
• [ ] events_big_cap_high_rate_callback - Stress test for events with a lot of users, deduplication enabled and high rate event with a big queue capacity using callback mode
• [ ] events_callback - Stress test for events with a lot of users and deduplication ENABLED in callback mode
• [ ] events_without_dedup - Stress test for events with a lot of users and deduplication DISABLED
• [ ] events_without_dedup_callback - Stress test for events with a lot of users and deduplication DISABLED using callback mode
• [ ] extended-reference-mode - Extended reference mode enabled
• [ ] large-request - Stress test with a 1 MB request payload
• [ ] no-tracing - Basic stress test, no tracing
• [ ] reload - Reload test over a long period of time at a constant rate of users
• [ ] step-jemalloc-tuning - Clone of the basic stress test for jemalloc tuning
• [ ] step-local-metrics - Field stats that are generated from the router rather than FTV1
• [ ] step-with-prometheus - A copy of the step test with the Prometheus metrics exporter enabled
• [x] step - Basic stress test that steps up the number of users over time
• [ ] xlarge-request - Stress test with 10 MB request payload
• [ ] xxlarge-request - Stress test with 100 MB request payload