1. Add `centipede` to `DEFAULT_ENGINES`.
2. Remove the `fuzzing_engines` attribute from `project.yaml`s if
redundant (i.e., all default engines are included in that YAML file).
3. Temporarily disable `centipede` on `c`/`c++` projects that previously
use all `DEFAULT_ENGINES` (200 projects did not specify
`fuzzing_engines` in `project.yaml`) so that we can gradually enable
centipede later them later.
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