Replace [string]::IsNullOrEmpty with -not in Azure storage cmdlets (#870)

[pavankadabala-png]

Applies the [string]::IsNullOrEmpty → -not quick-win from #870 (suggested by @FriedrichWeinmann) to the Azure storage cmdlets.

For a string operand, [string]::IsNullOrEmpty($x) is equivalent to -not $x, so this replaces the more verbose form:

# before
if (([string]::IsNullOrEmpty($AccountId) -eq $true) -or
    ([string]::IsNullOrEmpty($Container)) -or
    (([string]::IsNullOrEmpty($AccessToken)) -and ([string]::IsNullOrEmpty($SAS)))) {

# after
if ((-not $AccountId) -or
    (-not $Container) -or
    ((-not $AccessToken) -and (-not $SAS))) {

Files

• Get-D365AzureStorageFile
• Get-D365AzureStorageUrl
• Invoke-D365AzureStorageDownload
• Invoke-D365AzureStorageUpload

Notes

• Every operand here is a [string] parameter, so -not and [string]::IsNullOrEmpty are equivalent — they only differ for non-string values such as 0 or $false. I kept the original parentheses/grouping so the boolean logic is unchanged.
• Scope: limited to the Azure storage cmdlets @FriedrichWeinmann referenced. The same simplification applies to other string-parameter checks across the module — happy to follow up in a separate PR. I intentionally left sites where the operand is an object or external-command output (e.g. Get-MpComputerStatus, & $executable ...) unchanged, since -not is not equivalent there.

Refs #870

[FH-Inway]

@pavankadabala-png Thanks for the contribution, looks good. Would be great if you could follow up for other string parameter checks.