Allow setting logo for app registrations

**Related command**
`az ad app create`

**Is your feature request related to a problem? Please describe.**
Currently it is very unintuitive to add a logo image to a app registration.

**Describe the solution you'd like**
`--logo "@path/to/logo.png"`

**Describe alternatives you've considered**
Using the (Power)shell's HTTP client because `az rest` does not seem to work with images.

```
$graphJwt = az account get-access-token --resource-type ms-graph | ConvertFrom-Json -Depth 100
$headers = @{
"Authorization" = "Bearer $($graphJwt.accessToken)"
"Content-Type" = "image/png"
}
$bytes = [System.IO.File]::ReadAllBytes($logo)
Invoke-RestMethod -Uri "https://graph.microsoft.com/v1.0/applications/$($app.id)/logo" -Method PUT -Body $bytes -Headers $headers
```