update to catch Throwable for execute method

[kaibocai]

Issue describing the changes in this PR

resolves #295

Pull request checklist

• My changes do not require documentation changes
  • Otherwise: Documentation issue linked to PR
• My changes should not be added to the release notes for the next release
  • Otherwise: I've added my notes to release_notes.md
• My changes do not need to be backported to a previous version
  • Otherwise: Backport tracked by issue/PR #issue_or_pr
• I have added all required tests (Unit tests, E2E tests)

Additional information

• Need to test out on production, especially for durable functions.

Catching Exception will igore Error happend in java worker process or customer code. This resulted in host hanging up for 30mins and time out, since host never get chance to know that an Error happened in java worker. This is because Error won't be caught and it will break the current logics to response the host request through grpc.

Update to catch Throwable so that any Error type will also be caught and inform host through grpc.
Didn't re-throw the Throwable as there is not much difference, as long as we get this Error info passed back to host.