[storage] anvil-manage-server-storage CLI options must be cleaned up

[fabbione]

The CLI usage is confusing at best and it needs to be reworked to be easy to understand and consistent.

• drop the concept of --optical and --disk and rename both to --device. anvil already knows what type of device it is and how to act on it.
• do NOT attempt to map internal VM disk names with outside. For example:```Optical Drives:
• Target: [sda], boot: [02], ISO: [/mnt/shared/files/CentOS-Stream-9-latest-x86_64-dvd1.iso]
• Target: [sdb], boot: [03], ISO: [/mnt/shared/files/deploy1.iso]``` will never be correct, as internally they are seen as sr0 / sr1. Offer instead a simple sequence number: disk0 / disk1 / cdrom0 / cdrom1.. etc., this is true for all operations.
• convert options to actions. For example --add --grow --remove (that is not there), should become: "add --size XGB" (to add a new disk) "grow --size XGB" (to grow to absolute XGB) or "grow --size +XGB" (to grow XGB more, error out on -XGB as shrinking is not supported). Also, for add, --device should be optional add pick up the first slot. add should might need an option to specify the type: disk / cdrom.
• --storage-group should be optional if there is only one storage group.
• --insert should be explicit that the file has is not a path, but a name from available images