parse invocation errors as strings

[connorsmith256]

Feature or Problem

When detecting host call errors, the NIF is returning the raw bytes from the error. Now we parse as a string before returning

Related Issues

Fixes #606

Release Information

Next

Consumer Impact

Much more clear error messages on host calls

Testing

Manual Verification

Tested manually with make run:

• started the HTTP server provider
• started the XKCD actor
• linked them
• invoked the XKCD actor, which tries to call the HTTP client provider. This isn't running, so the host generates an error, which is now parsed as a string:

{"error":"actor: sending req: Host send error Host call function failed: Invocation not authorized: missing link definition for wasmcloud:httpclient on default"}