SERVER-65964 Add documentation on burn_in_tags and burn_in_tests

docs/evergreen-testing/README.md

@@ -2,6 +2,8 @@
 
 Documentation about how MongoDB is tested in Evergreen.
 
+* [Burn_in_tags](burn_in_tags.md)
+* [Burn_in_tests](burn_in_tests.md)
 * [Configuration for Evergreen Integration](configuration.md)
 * [Task Timeouts](task_timeouts.md)
 * [Task Generation](task_generation.md)

docs/evergreen-testing/burn_in_tags.md

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+# burn_in_tags
+
+## What it is
+
+Similar to [burn_in_tests](burn_in_tests.md), `burn_in_tags` also detects the javascript tests
+(under the [jstests directory](https://github.com/mongodb/mongo/tree/master/jstests))
+that are new or have changed since the last git command and then runs those tests in repeated
+mode to validate their stability. But instead of running the tests on their original build
+variants, `burn_in_tags` runs them on the burn_in build variants that are generated separately.
+
+## How to use it
+
+You can use `burn_in_tags` on evergreen by selecting the `burn_in_tags_gen` task when creating a patch.
+The burn_in build variants, i.e., `enterprise-rhel-80-64-bit-inmem` and `enterprise-rhel-80-64-bit-multiversion`
+will be generated, each of which will have a `burn_in_tests` task generated by the
+[mongo-task-generator](https://github.com/mongodb/mongo-task-generator). `burn_in_tests` task, a
+[generated task](task_generation.md), may have multiple sub-tasks which run the test suites only for the
+new or changed javascript tests (note that a javascript test can be included in multiple test suites). Each of
+those tests will be run 2 times minimum, and 1000 times maximum or for 10 minutes, whichever is reached first.

docs/evergreen-testing/burn_in_tests.md

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+# burn_in_tests
+
+## What it is
+
+`burn_in_tests` detects the javascript tests (under the
+[jstests directory](https://github.com/mongodb/mongo/tree/master/jstests)) that are new or have changed
+since the last git command and then runs those tests in repeated mode to validate their stability.
+
+## How to use it
+
+You can use `burn_in_tests` on evergreen by selecting the `burn_in_tests_gen` task when creating a patch,
+since `burn_in_tests` task is a [generated task](task_generation.md) generated by the
+[mongo-task-generator](https://github.com/mongodb/mongo-task-generator).
+`burn_in_tests` task will be generated on each of the applicable build variants, and
+may have multiple sub-tasks which run the test suites only for the new or changed javascript tests (note
+that a javascript test can be included in multiple test suites). Each of those tests will be run 2 times
+minimum, and 1000 times maximum or for 10 minutes, whichever is reached first.
+
+You can also use `burn_in_tests` locally from within the [mongo repo](https://github.com/mongodb/mongo)
+by running the script `python buildscripts/burn_in_tests.py`. For more information about this usage, you can
+run `python buildscripts/burn_in_tests.py --help`.