zpm: make render_zar_yaml non-private
zpm: make render_zar_yaml non-private

It had a few callers and I'm not sure it needs to be private.

zerovm/zerovm-cli,zerovm/zpm,zerovm/zerovm-cli,zerovm/zerovm-cli,zerovm/zpm,zerovm/zpm,zerovm/zerovm-cli,zerovm/zpm,zerovm/zpm,zerovm/zerovm-cli,zerovm/zerovm-cli,zerovm/zpm