There were some linguering bugs with these types from the recent change
to require object type args with the '$' for the shape, as well as
array with args.ts with the typeset still around that existing tests
were skirting around. Added more tests to make tests more robust!

These were found thanks to a new 'integration.test.js' test suite
I added. It's already proving its usefulness!

This commit also removes the value from RtvError's message property
in case it happens to contain sensitive information. Please see the
note on the `RtvError#path` property.