[feature request] Pass certificate and key file contents instead of file path

[Siecje]

Is your feature request related to a problem? Please describe.

I'm loading the certificate to get the common name. I'd like to pass the contents of the certificate and key file when provisioning.

Describe the solution you'd like

For azure.iot.device.X509 to accept the file contents instead of the file paths.

Describe alternatives you've considered

My current work around is to create temp files.