Documentation needed to run web integration tests locally

I can't find documentation for running any of these configurations locally:

```
Linux web_long_running_tests_1_5
Linux web_long_running_tests_2_5
Linux web_long_running_tests_3_5
Linux web_long_running_tests_4_5
Linux web_long_running_tests_5_5
```

Ideally a failure for any of these tests should print repro instructions in the failure logs.

Helpful documentation would include:

- How to run a single test locally.
- How to run an entire test shard locally.

Start by locating the web_long_running_tests_1_5 through web_long_running_tests_5_5 configurations and reading the existing web integration test documentation and test-running entry points. Document how to run one test and a complete shard locally, and ensure failures provide reproducible instructions in their logs.

Written by the indexing model from the issue text.