Should be a slick way to store and retrieve a PSCredential object from a Key Vault Secret

## Description of the new feature

Need an easy way to store and retrieve a PSCredential object. For example:

$creds = Get-Credential
Set-AzKeyVaultSecret -VaultName $vaultName -name $secretName -PsCredential $creds

and

$credsRetrieved = Get-AzKeyVaultSecret -vaultName $VaultName -name $secretName -PsCredential

## The Existing Mechanism

Here is the clunky way I have come up with to do it:

$Creds = Get-Credential -Message "$msg"
# create an vertical tab-delimited string from the values entered
$secretstring = $Creds.GetNetworkCredential().UserName + "`v" + $Creds.GetNetworkCredential().Password
$secretvalue = ConvertTo-SecureString $secretstring -AsPlainText -Force
# store in Key Vault
Set-AzKeyVaultSecret -VaultName $VaultName -name $DomainSecretName -secretvalue $secretvalue

and

$secretValueParts = (Get-AzKeyVaultSecret -vaultName $VaultName -name $DomainSecretName).SecretValueText -Split "``v"
$password = ConvertTo-SecureString $secretValueParts[1] -AsPlainText -Force
$Credential = New-Object System.Management.Automation.PSCredential ($secretValueParts[0], $password)