Let's create a stream for RHCOS based on RHEL 10 nightlies.

The goal is to get this into OCP 4.20 and 4.21 release payloads.

OCP will not use it by default until OCP 4.22 and RHEL 10.2, however we want it to be in the payload so that by 4.20 GA we can ask all teams to validate that they've tested a cluster with RHEL10 based RHCOS by applying a simple'ish MachineConfig.

After branching 4.21 from master we can move the default to RHCOS 10 which will track toward 10.2 GA content for 4.22.