Provide option to set the boot order for a vm in Cloudstack

### The required feature described as a wish

As a User/Admin/Operator I would like to make my vm to boot from a Pixe/Network server

Currently, we have option to boot into hardware mode in cloudstack

Also, all hypervisors provide an option to change the boot order type

Kvm,

we need to edit the XML and set the boot order type

```

hvm
/usr/lib/xen/boot/hvmloader

```

vmware

xen


Proxmox

The issue identifies CloudStack and boot-order behavior across KVM, VMware, Xen, and Proxmox, but names no source files, tests, or API entry points. Start by locating the VM boot-configuration paths for the supported hypervisors and compare their existing hardware-boot handling. Done should include a defined user-facing boot-order option implemented consistently where supported, with coverage for the affected hypervisors.

Written by the indexing model from the issue text.