Configdrive/storage repository issue on XCP-ng

### problem

Issue No1:
In case of failed deployments there are unused storage repositories left behind.

`example:
**xe vdi-list uuid=f16e0133-2074-49af-a393-1bb9fa007fb5**
uuid ( RO) : f16e0133-2074-49af-a393-1bb9fa007fb5
name-label ( RW): i-2-24-VM.iso
name-description ( RW):
sr-uuid ( RO): **608c63b9-9c12-bf6a-8d28-f2bc7d01d343**
virtual-size ( RO): 409600
sharable ( RO): false
read-only ( RO): true

**xe sr-list name-label=i-2-24-VM-CONFIGDRIVE-ISO**
uuid ( RO) : 12b1e17a-fb1c-d99f-451c-baf035b822f2
name-label ( RW): i-2-24-VM-CONFIGDRIVE-ISO
name-description ( RW): 10.1.32.4:/acs/secondary/ref-trl-6095-x-Mu24/ref-trl-6095-x-Mu24-sec2/configdrive
host ( RO):
type ( RO): iso
content-type ( RO): iso

uuid ( RO) : **608c63b9-9c12-bf6a-8d28-f2bc7d01d343**
name-label ( RW): i-2-24-VM-CONFIGDRIVE-ISO
name-description ( RW): 10.1.32.4:/acs/secondary/ref-trl-6095-x-Mu24/ref-trl-6095-x-Mu24-sec2/configdrive
host ( RO):
type ( RO): iso
content-type ( RO): iso

uuid ( RO) : 222f3918-75e1-99f9-f7f2-e63d714c130f
name-label ( RW): i-2-24-VM-CONFIGDRIVE-ISO
name-description ( RW): 10.1.32.4:/acs/secondary/ref-trl-6095-x-Mu24/ref-trl-6095-x-Mu24-sec2/configdrive
host ( RO):
type ( RO): iso
content-type ( RO): iso`

As you see above just one storage repository is being used for the ISO file.
This has no functional impact but leaves something unused behind.

Issue No 2:
Within a storage repository which name is specified to one particular VM you can see all the iso files from all the other VMs since they are located in the same secondary storage. Why not have one general storage repository like "VM-CONFIGDRIVE-ISO" to avoid both issues?

### versions

ACS: 4.20.1
XCP-ng: 8.2

### The steps to reproduce the bug

1. Build a couple of VMs where you have limited resources available on the hypervisors.
2.

3. The hypervisor still has been selected for deployments but failed from hypervisor side
4. Several attempts have happened
```
cat /var/log/cloudstack/management/management-server.log | grep job-117 | grep 'VM start attempt'
2025-10-28 14:22:19,361 DEBUG [c.c.v.ClusteredVirtualMachineManagerImpl] (Work-Job-Executor-42:[ctx-a1bf013f, job-117/job-118, ctx-520420a9]) (logid:67fb25c7) VM start attempt #1
2025-10-28 14:22:24,301 DEBUG [c.c.v.ClusteredVirtualMachineManagerImpl] (Work-Job-Executor-42:[ctx-a1bf013f, job-117/job-118, ctx-520420a9]) (logid:67fb25c7) VM start attempt #2
2025-10-28 14:22:25,371 DEBUG [c.c.v.ClusteredVirtualMachineManagerImpl] (Work-Job-Executor-43:[ctx-34843ad3, job-117/job-119, ctx-605dae51]) (logid:67fb25c7) VM start attempt #1
2025-10-28 14:22:28,159 DEBUG [c.c.v.ClusteredVirtualMachineManagerImpl] (Work-Job-Executor-43:[ctx-34843ad3, job-117/job-119, ctx-605dae51]) (logid:67fb25c7) VM start attempt #2
```
5. For each attempt a storage repository has been created. Every time an ISO file as well. On failed attempt the ISO file has been removed but the storage repository not.
6. Once the VM finally got deployed you'll end up with multiple storage repositories, used and unused once with the same name.

### What to do about it?

Option 1: Besides removing the ISO file do also remove the storage repository on failed deployments.
Option 2: Use one general storage repository for all ISO files.

Start by reproducing the failed deployment retries described for ACS 4.20.1 with XCP-ng 8.2, using the management-server.log VM start attempts and the xe sr-list/xe vdi-list output. Compare the cleanup after each failed attempt and determine whether the implementation should remove the unused storage repository or share one repository for config-drive ISOs. Done means failed attempts leave no unused repositories and successful deployments retain their ISO access.

Written by the indexing model from the issue text.