Sharing my local test runner script for CI-like test app build and execution (#35625)

* Add a test runner for convenient python runs

* Add some documentation

* Restyle

* Update requirements

* Use local build platforms, to maybe be able to run under darwin

* Use local build platforms, to maybe be able to run under darwin

* Fix typos

* More typo fixes

* Restyle

* Make platform name actually work

* Restyled by prettier-markdown

* Fix linter

* Add license

---------

Co-authored-by: Andrei Litvin <andreilitvin@google.com>
Co-authored-by: Restyled.io <commits@restyled.io>

Author: 3 people

docs/testing/python.md

@@ -637,6 +637,18 @@ format, use the `--load-from-env` flag with the `run_python_tests.py` runner.
 Ex:
 `scripts/run_in_python_env.sh out/venv './scripts/tests/run_python_test.py --load-from-env /tmp/test_env.yaml --script src/python_testing/TC_ICDM_2_1.py'`
 
+## Running ALL or a subset of tests when changing application code
+
+`scripts/tests/local.py` is a wrapper that is able to build and run tests in a
+single command.
+
+Example to compile all prerequisites and then running all python tests:
+
+```
+./scripts/tests/local.py build         # will compile python in out/pyenv and ALL application prerequisites
+./scripts/tests/local.py python-tests  # Runs all python tests that are runnable in CI
+```
+
 ## Defining the CI test arguments
 
 Below is the format of the structured environment definition comments: