Populate metta test answer files

[stassa]

mettalog tests in metta-testuite development branch take their correct results from .answer files, one for each test file. Answer files simply store the output of the test scripts as output by metta (i.e. Hyperon-experimental).

To avoid re-generating answer files every time the tests are run, it would be useful to generate them all in one go and include them with test files. This has been done only for a minority of tests in metta-testuite.

This issue is to track the progress of generating answer files for mettalog by generating the output of tests with Hyperon-experimental.