Review and incorporate SSC datamodel in roman_datamodels

[stscijgbot-rstdms]

Issue RCAL-976 was created on JIRA by Nadia Dencheva:

We received a datamodel from SSC (a wheel) for the G2DP pipeline. We've been asked to incorporate it in out roman_datamodels package to have one way to open all Roman files.

[stscijgbot-rstdms]

Comment by Nadia Dencheva on JIRA:

The SSC code should be kept internal to STScI only and delivered to OPS with build deliveries.

There should be hooks in roman_datamodels to import the code if available and open SSC files. Ideally the open command should work transparently on SOC and SSC files.