The vCenter Server name is in the Uid property. You can use the string Split() method to extract the vCenter Server name:
Get-VM | Select-Object Name,@{N="vCenter";E={$_.Uid.Split('@')[1].Split(':')[0]}}
Get-VMHost | Select-Object Name,@{N="vCenter";E={$_.Uid.Split('@')[1].Split(':')[0]}}