Warn that integration tests are not run automatically (#162626)

## Pre-launch Checklist

- [x] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [x] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [x] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [x] I signed the [CLA].
- [ ] I listed at least one issue that this PR fixes in the description
above.
- [ ] I updated/added relevant documentation (doc comments with `///`).
- [ ] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [x] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [x] All existing and new tests are passing.

dev/integration_tests/README.md

@@ -18,3 +18,7 @@ For example:
 ```sh
 flutter drive -t lib/keyboard_resize.dart --driver test_driver/keyboard_resize_test.dart
 ```
+
+## New tests require new CI runner
+Adding code to this directory will not automatically cause it to be run by any already existing ci tooling.
+This directory is intentinally a "choose your own adventure" piece of tooling.