changed install_katex.sh to install_docs_reqs.sh, added install doxygen (#77907)
Fixes #77399
Increase CI stability by migrating a dependency to Docker to minimize risk of failure in installation. Installing doxygen in install_docs_reqs.sh instead of the cpp docs script.
**Test Plan**: cpp docs build passes
Pull Request resolved: https://github.com/pytorch/pytorch/pull/77907
Approved by: https://github.com/seemethere, https://github.com/janeyx99
