Validate service offering name for ( Compute, System, Disk offerings)

### The required feature described as a wish

Currently cloudstack is allowing to create offering with the same name for Compute, System, Disk offerings

Where as Cloudstack validates name for (Backup , Network and VPC offerings )

for compute offerings we can have the same name

Expected behaviour

It would be great if Cloudstack can validate the service offering name for Compute, System, Disk offerings in order to maintain consistency across

Start by locating the existing name validation for Backup, Network, and VPC offerings, then trace the creation paths for Compute, System, and Disk offerings. Compare the behaviors and add coverage for duplicate names; done means those offering types consistently reject duplicates as described.

Written by the indexing model from the issue text.