* Groundwork to enable python format checks (via yapf) as part of the CI.

With this change:
 * we are set up to use yapf as part of the docker container
 * pigweed patch is updated to use the google Python style (pep8 with indent of 2 spaces)
 * some documentation updates.

The code still needs to be formatted, and then the Python formatting check will be turned on as part of ci.

BUG=http://b/194404216

* Format all the code.

Once this change is merged, we will turn on Python formatting check as
part of the CI.

* minor formatting update.

* Turn on Python formatting checks as part of CI.

Also, add an option to fix the formatting via the test_code_style.sh
script.

BUG=http://b/194404984 and http://b/194404216