Add installer.flare-vm.vm

Nobody has claimed this yet.

### Details

@mandiant/vms the `installer.vm` package has been installed >278k times in the last year, as you can see in [MyGet](https://www.myget.org/feed/vm-packages/package/nuget/installer.vm). As we are not using this package in the CI or for testing, this means that **Commando VM and FLARE-VM have been installed >278k times (together) last year!** But sadly we don't have a way to differentiate how many times every of the projects have been installed separately.

I propose to add a `installer.flare-vm.vm` package (and if commando VM wishes also a `installer.commando-vm.vm` package) that requires the common installer and use the project specific one in the project installers. This will allow us to know the number of individual downloads. @mandiant/vms what do you think? Is there anything that could be moved to the project installer so that they are not only a wrapper but help for example simplify the installation scripts?

For context: FLARE-VM migrated to use the `debloat.vm` and `installer.vm` packages shared with Commando VM so that both proects benefit from improvements in https://github.com/mandiant/flare-vm/pull/513. We removed the `flarevm.installer.vm` package from VM-Packages in https://github.com/mandiant/VM-Packages/pull/752 and we are going to remove it soon from MyGet (tracked in https://github.com/mandiant/VM-Packages/issues/907).

Start by inspecting the existing installer.vm package and the FLARE-VM project installer references mentioned in the issue. Determine how a project-specific installer package can require the shared installer while preserving separate download counts. Done means the FLARE-VM installer uses installer.flare-vm.vm and the package metadata and installation flow are validated.

Written by the indexing model from the issue text.