Add tests and futures motivated by HPO's use of these features

[lydia-duncan]

Covers:

• taking and returning arrays of c_ptrConst(c_char) in exported functions
• accepting arguments of arrays of strings in exported functions
• throwing from hash functions in script-like .chpl files
• throwing from hash functions in script-like .chpl files due to calling functions that throw
• calling functions with ref intent for the this argument from hash functions
• explicitly declaring the hash function to have ref intent for its this argument
• throwing from hash functions in explicit modules

Checked a fresh checkout of the hash tests behaved as expected. The Python interop tests worked locally