Fixes # .

Summary/Motivation:

This resolves an issue with the SAS interface where the SAS session was being started in the interface __init__.py. This meant that any time the interface was created it immediately tried to connect - which, if you are offline, hung until the connection timed out (~10 seconds). With these changes (and some changes with how SAS tests are skipped), running the tests offline only hits the timeout once (and not a dozen times).

Changes proposed in this PR:

• Move the logic to start the SAS session into a helper method
• Only start the SAS session when needed (for the available() check or for solve())
• Update the SAS tests to minimize the number of times available() needed to be checked.

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