Changes the configuration to regroup all includes. The include groups
will be (in this order):
1. (in .cc): Include of the corresponding header
2. Includes of C++ standard library headers
3. Includes of other external headers
4. Includes of local headers
Externally developed dependencies which have been imported ("vendored") into
this repository. These dependencies come with their own licenses and whatever
else.
Code that is developed inside of this repository, but released to an external
repository via Copybara.