Fix hardcoded DiskNumber=2 in CreateADPDC.ps1 causing deployment failures on certain VM configurations

## Issue Description

### Problem
The DSC script `CreateADPDC.ps1` in the HPC Pack template contains hardcoded references to `DiskNumber = 2` for data disk configuration. This causes deployment failures when:

1. VMs have different disk numbering schemes
2. Only one data disk is attached (appears as Disk 1 instead of Disk 2)
3. VM sizes with different network adapter configurations affect disk enumeration

### Affected Code Location
File: `SharedResources/Generated/CreateADPDC.ps1.zip` → `CreateADPDC.ps1`

**Lines 46-56:**
```powershell
xWaitforDisk Disk2
{
DiskNumber = 2 # ← HARDCODED VALUE
RetryIntervalSec =$RetryIntervalSec
RetryCount = $RetryCount
}
xDisk HPCDataDisk
{
DiskNumber = 2 # ← HARDCODED VALUE
DriveLetter = "F"
FSLabel = 'HPCData'
}
```

### Impact
- **Deployment Failures**: DSC extension fails when expected Disk 2 doesn't exist
- **VM Size Compatibility**: Affects Standard_D2s_v3, Standard_HB120rs_v3, and other VM sizes
- **User Experience**: Forces manual intervention and workarounds

### Error Examples
```
DSC Extension Error: Cannot find disk with number 2
VM Configuration: OS Disk (Disk 0) + Data Disk (Disk 1) = Only 2 disks total
Expected by Script: Disk 2 (which doesn't exist)
```

### Proposed Solution

Replace hardcoded disk numbers with dynamic disk detection:

```powershell
# Suggestion, instead of hardcoded DiskNumber = 2.
xWaitforDisk DataDisk
{
DiskNumber = (Get-Disk | Where-Object {$_.PartitionStyle -eq 'RAW' -and $_.Size -gt 30GB} | Select-Object -First 1).Number
RetryIntervalSec = $RetryIntervalSec
RetryCount = $RetryCount
}
xDisk HPCDataDisk
{
DiskNumber = (Get-Disk | Where-Object {$_.PartitionStyle -eq 'RAW' -and $_.Size -gt 30GB} | Select-Object -First 1).Number
DriveLetter = "F"
FSLabel = 'HPCData'
}
```

**Alternative Approach:**
Add a parameter to make disk number configurable:

```powershell
param(
[Parameter(Mandatory)]
[String]$DomainName,

[Parameter(Mandatory)]
[System.Management.Automation.PSCredential]$Admincreds,

[Int]$DataDiskNumber = 1, # ← NEW PARAMETER WITH DEFAULT

[String[]]$DnsForwarder = @("8.8.8.8"),
[Int]$RetryCount = 20,
[Int]$RetryIntervalSec = 30
)
```

### Environment Details
- **Template**: Azure HPC Pack 2019 Update 3
- **VM Sizes Affected**: Standard_D2s_v3, Standard_HB120rs_v3, others
- **Azure Region**: eastus (and likely others)
- **Deployment Method**: ARM/Bicep templates with DSC extension

### Workaround Used
Currently using modified local copy of CreateADPDC.ps1 with `DiskNumber = 1` for affected deployments.

### Request
Please update the DSC script to use dynamic disk detection or configurable disk numbers to improve compatibility across different VM configurations and deployment scenarios.

---

**Repository**: https://github.com/Azure/hpcpack-template
**File**: SharedResources/Generated/CreateADPDC.ps1.zip
**Priority**: Medium (affects deployment reliability)
**Labels**: bug, enhancement, dsc, deployment