docs: setup docs for C code (#23262)

* add breathe and doxygen

* add sphinx-breathe c docs generation
* add c docs to site

* built in docker

* build base image first

* namespace cleanup

* Revert "build base image first"

This reverts commit 4c44c02ffb93b3f0bc3968f2ee1fdc64faa25608.

* its in the dockerfile

Co-authored-by: Willem Melching <willem.melching@gmail.com>
old-commit-hash: 9f70bea964

docs/docker/Dockerfile

@@ -34,6 +34,7 @@ COPY ./*.md ${OPENPILOT_PATH}/
 
 RUN scons -j$(nproc)
 
+RUN apt update && apt install doxygen -y
 COPY ./docs ${OPENPILOT_PATH}/docs
 RUN git init .
 WORKDIR ${OPENPILOT_PATH}/docs