Use FIPS-Compliant Sha256 hash function in QOS functions in AzureSMCmdlet and AzureRmCmdlet

[markcowl]

Description

Short term fix for #3642.

• Use Sha256CryptoProvider or Sha256Cng directly in Qos handling code here: https://github.com/Azure/azure-powershell/blob/dev/src/Common/Commands.Common/MetricHelper.cs#L210
• Verify correct execution of general cmdlets (Get-AzureRmSubscription, Get-AzureRmStorageAccount) with FIPS mode enabled

Cost: 2

[markcowl]

Fixed