Does Deploy-AzTemplate.ps1 require PowerShell Core 6.x?

Deploy-AzTemplate.ps1 requires PowerShell Az.

PowerShell Az supports Windows PowerShell and PowerShell Core (according to [Introducing the new Azure PowerShell Az module](https://docs.microsoft.com/en-us/powershell/azure/new-azureps-module-az?view=azps-2.4.0)):
> With the Az module, Azure PowerShell is now compatible with PowerShell 5.1 on Windows and PowerShell Core 6.x and later on all supported platforms - including Windows, macOS, and Linux.

Does Deploy-AzTemplate.ps1 require PowerShell Core 6.x?

PR #5972 added a call to `Split-Path $TemplateFile -LeafBase` which is resulting in me getting `Split-Path : A parameter cannot be found that matches parameter name 'LeafBase'` when I run Deploy-AzTemplate.ps1 using Execute Script in Visual Studio 2017 in a Azure Resource Group Project which is executing in Windows PowerShell.

Open Deploy-AzTemplate.ps1 and inspect the Split-Path -LeafBase call introduced by PR #5972. Compare the script's requirements with the Windows PowerShell environment used by Execute Script in Visual Studio 2017 and the PowerShell Core versions supported by Az. Done means the supported runtime requirement is established and the script's compatibility behavior is verified or documented.

Written by the indexing model from the issue text.