[doc] Move CI installation info to documentation

MANIFEST.in

doc/ci.rst

doc/index.rst

doc/links.rst

doc/linux.rst

doc/macos-ci-install/admin-install.sh

doc/macos-ci-install/datetime.sh

doc/macos-ci-install/idiap-host.sh

doc/macos-ci-install/install-gitlab-runner.sh

doc/macos-ci-install/install-homebrew.sh

doc/macos-ci-install/install-sdk.sh

doc/macos-ci-install/setup-paths.sh

doc/macos-ci-install/system-update.sh

doc/macos-ci-install/xcode-cli-tools.sh

doc/macos.rst