Fix TSP load_script not checking write_termination for long scripts

[raywcm]

Problem

TSP devices have a max write of approximately 1000 characters before a write_termination character must exist. load_script() writes the entire script body in a single self.write() call, which fails when the script exceeds the max write size.

Fix

Extract the loadscript command into a variable so the caller can check the length and insert write_termination characters as needed before the max limit is exceeded.

Closes #500

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[raywcm]

I have read the CLA Document and I hereby sign the CLA

[v12ganesh]

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[nfelt14]

Closing this PR based on a lack of interaction and updates.