[64-bit ints] Add script_tests for getint coverage

Summary: Currently, all the getint calls in interpreter.cpp don't have coverage for very large integers that might overflow.

Test Plan: ninja check

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D17290