Continuing #8801.
The third round of rolling out `Centipede`, which contains the following
10 projects (some are not from within Google):
1. `bloaty`,
2. `double-conversion`,
3. `zopfli`,
4. `guetzli`,
5. `jsonnet`,
6. `astc-encoder`,
7. `piex`,
8. `wuffs`,
9. `arrow`,
10. `myanmar-tools`.
Projects are selected because they are `C++` projects.
These projects were tested and it was found that their use
of MSAN does not work on Ubuntu 20.04. Therefore their use of
MSAN is being disabled.
Related: #6180
* [presubmit] Enforce language attribute in projectt.yaml to be always set.
* Update documentation, better presubmit check, new project template.
* add docstring to templates.py
* Add example values in the project.yaml template and remove python value for now
* Add "project: c++" to 256 projects
* format
* Add labels and selective_unpack sections to the presubmit check
* fix incorrect auto_ccs format in three projects
* fix nss emails after rebase
Dongge Liu