We have several test suites that shut down shards and verify retryable writes still work (e.g. concurrency_sharded_with_stepdowns and retryable_writes_jscore_stepdown_passthrough), but none that shut down routers, which should be supported by retryable writes as well. There have been several bugs such a suite could have found, like SERVER-51329, SERVER-55648, and SERVER-53624.

1. Create a new yml for routerFailures
2. Create a new testFixture for suite.
3. Create testfile(*.js) files as necessary to test it
4. Link the task from evergreen.yml