Added 2 mermaid diagrams to demonstrate entity caching and entity cache invalidation

[andrewicarlson]

This PR adds two Mermaid diagrams demonstrating Entity Caching using a Price entity, and then a cache invalidation workflow. These are similar to the diagrams we used in the GraphQL Summit 2024 keynote, but I had to make some styling concessions to fit within the constraints of Mermaid (comments inline in the file below)

[svc-apollo-docs]

✅ Docs Preview Ready

No new or changed pages found.

[github-actions]

@andrewicarlson, please consider creating a changeset entry in /.changesets/. These instructions describe the process and tooling.

[router-perf]

CI performance tests

• connectors-const - Connectors stress test that runs with a constant number of users
• 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
• 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

[andrewicarlson]

Similar to the above, I found that Mermaid didn't support the delete sequence in Markdown, so I kludged together this solution for crossing out the individual characters.

[andrewicarlson]

Here are screenshots of the two diagrams rendered on the page using the docs-rewrite repo locally.

[Meschreiber]

These diagrams are such a great value add, ty @andrewicarlson ! I've made some suggestions to give them context and clarify the arrow directions in the invalidation diagram, but otherwise LGTM!