Add JSON output support to Invoke-GraphRequest

[adamedx]

When building new commands on top of Invoke-GraphRequest, it may be necessary to get the response in JSON form (e.g. for interop with other tools that take in JSON). A workaround today is to convert the deserialized output back to JSON (e.g. ConvertTo-JSON, but that's obviously inefficient.

Something like a -Json option on the command would meet the requirement here.
AB#6854