Simplify device path on boot with udev

While prototyping Bottlerocket, I discovered it doesn't recognize additional EBS volumes specified through Block device mappings on Xen. For example, launching the same AMI on t2.medium (Xen) and t3.medium (Nitro) with "DeviceName=/dev/xvdcz": On Nitro, the device appears at /dev/nvme1n1 and /dev/disk/by-ebs-id/xvdcz. On Xen, it appears at /dev/xvdcz. In the prototype, the xvdcz volume is…