Ui : Improve the error log message

### The required feature described as a wish

As a Admin /Operator I would like to see the correct error message if the instance conversion from vmware to kvm fails

Steps to reproduce the issue

1. Select a kvm host which does not have the virt-v2v installed

The following exception is thrown in the UI > this not clear to the end user

2. On checking the logs

```

2026-04-13 06:32:30,120 ERROR [o.a.c.v.UnmanagedVMsManagerImpl] (API-Job-Executor-85:[ctx-de7abe65, job-145, ctx-d94fe1bb]) (logid:03b36fd8) The host Host {"id":2,"name":"ref-trl-6210-k-Mr9-kiran-chavala-kvm2","type":"Routing","uuid":"ee80e6e2-2e52-4dce-b554-6af6027303c6"} doesn't support conversion of instance i-2-14-VM from VMware to KVM due to: Cannot convert the instance from VMware using VDDK on host 10.1.34.207. Please make sure virt-v2v, nbdkit-vddk and a valid VDDK library directory are available on the host.
2026-04-13 06:32:30,120 ERROR [o.a.c.v.UnmanagedVMsManagerImpl] (API-Job-Executor-85:[ctx-de7abe65, job-145, ctx-d94fe1bb]) (logid:03b36fd8) Error importing VM: The host Host {"id":2,"name":"ref-trl-6210-k-Mr9-kiran-chavala-kvm2","type":"Routing","uuid":"ee80e6e2-2e52-4dce-b554-6af6027303c6"} doesn't support conversion of instance i-2-14-VM from VMware to KVM due to: Cannot convert the instance from VMware using VDDK on host 10.1.34.207. Please make sure virt-v2v, nbdkit-vddk and a valid VDDK library directory are available on the host. com.cloud.utils.exception.CloudRuntimeException: The host Host {"id":2,"name":"ref-trl-6210-k-Mr9-kiran-chavala-kvm2","type":"Routing","uuid":"ee80e6e2-2e52-4dce-b554-6af6027303c6"} doesn't support conversion of instance i-2-14-VM from VMware to KVM due to: Cannot convert the instance from VMware using VDDK on host 10.1.34.207. Please make sure virt-v2v, nbdkit-vddk and a valid VDDK library directory are available on the host.
at org.apache.cloudstack.vm.UnmanagedVMsManagerImpl.checkConversionSupportOnHost(UnmanagedVMsManagerImpl.java:2110)
at org.apache.cloudstack.vm.UnmanagedVMsManagerImpl.importUnmanagedInstanceFromVmwareToKvm(UnmanagedVMsManagerImpl.java:1704)
at org.apache.cloudstack.vm.UnmanagedVMsManagerImpl.baseImportInstance(UnmanagedVMsManagerImpl.java:1366)
at org.apache.cloudstack.vm.UnmanagedVMsManagerImpl.importVm(UnmanagedVMsManagerImpl.java:1517)

2026-04-13 06:32:30,130 ERROR [c.c.a.ApiAsyncJobDispatcher] (API-Job-Executor-85:[ctx-de7abe65, job-145]) (logid:03b36fd8) Unexpected exception while executing org.apache.cloudstack.api.command.admin.vm.ImportVmCmd java.lang.NullPointerException: Cannot invoke "com.cloud.vm.ImportVMTaskVO.setUpdated(java.util.Date)" because "importVMTaskVO" is null
at org.apache.cloudstack.vm.ImportVmTasksManagerImpl.updateImportVMTaskErrorState(ImportVmTasksManagerImpl.java:166)
at org.apache.cloudstack.vm.UnmanagedVMsManagerImpl.importUnmanagedInstanceFromVmwareToKvm(UnmanagedVMsManagerImpl.java:1768)''

```

Expected behaviour

The following error message should be shown in the ui

```
Cannot convert the instance from VMware using VDDK on host 10.1.34.207. Please make sure virt-v2v, nbdkit-vddk and a valid VDDK library directory are available on the host.
```