docs: document rust ci datadog queries and dashboard

.gitignore

@@ -0,0 +1 @@
+.DS_Store

service-catalog/rust-ci/README.md

@@ -15,3 +15,7 @@ The [terraform/rust-ci] module provisions some resources used by the CI:
 [terraform/rust-ci]: https://github.com/rust-lang/simpleinfra/tree/master/terraform/rustc-ci
 [rust-lang/rust]: https://github.com/rust-lang/rust/
 [workflows]: https://github.com/rust-lang/rust/tree/master/.github/workflows
+
+## How-to Guides
+
+- [How to monitor CI time](./how-to-monitor-ci-time.md)

service-catalog/rust-ci/how-to-monitor-ci-time.md

@@ -0,0 +1,17 @@
+# How to monitor CI time
+
+This guide explains how to monitor the time taken by the Rust CI.
+You can monitor how long the Rust CI takes to run and other useful insights
+by looking at the
+[Datadog CI visibility](https://app.datadoghq.com/dash/integration/ci_app_pipelines?fromUser=false&refresh_mode=sliding&tpl_var_branch_name%5B0%5D=auto&from_ts=1731505840947&to_ts=1732110640947&live=true)
+dashboard.
+
+## Useful queries
+
+- [Average CI time](https://app.datadoghq.com/ci/pipeline-executions?query=ci_level%3Apipeline%20%40git.branch%3Aauto%20%40ci.status%3Asuccess&agg_m=%40duration&agg_m_source=base&agg_t=avg&cipipeline_explorer_sort=time%2Cdesc&fromUser=false&index=cipipeline&mode=sliding&saved-view-id=2722979&viz=timeseries&start=1730814194903&end=1732110194903&paused=false)
+
+  ![datadog screenshot](./average-ci-time.png)
+
+- [CI time of a single job](https://app.datadoghq.com/ci/pipeline-executions?query=ci_level%3Ajob%20%40git.branch%3Aauto%20%40ci.job.name%3A%22auto%20-%20dist-x86_64-msvc-alt%22%20%40ci.status%3Asuccess&agg_m=%40duration&agg_m_source=base&agg_t=avg&colorBy=meta%5B%27ci.job.name%27%5D&colorByAttr=meta%5B%27ci.job.name%27%5D&currentTab=trace&fromUser=false&graphType=flamegraph&index=cipipeline&spanID=16171819458268483629&spanViewType=logs&viz=timeseries&start=1729506323634&end=1732098323634&paused=false)
+
+  ![datadog screenshot](./ci-time-by-job.png)