[ci] Add ROOT CI workflow

.github/workflows/all-branches.yml

.github/workflows/buildroot.yml

.github/workflows/rootci-installers/build_root.py

.github/workflows/rootci-installers/build_utils.py

.github/workflows/rootci-installers/buildconfig/global.txt

.github/workflows/rootci-installers/buildconfig/mac12.txt

.github/workflows/rootci-installers/buildconfig/ubuntu18.txt

.github/workflows/rootci-installers/buildconfig/ubuntu20.txt

.github/workflows/rootci-installers/buildconfig/windows.txt

.github/workflows/testsecurity.yml