Handle all exceptions as non-retryable when TEMPORAL_DEBUG is set

[mobiletoly]

Is your feature request related to a problem? Please describe.
By default all exceptions are Retryable in workflows/activities and it makes troubleshooting much harder when we have to deal with a core exceptions such as NullPointerException, InvalidArgumentException, SQL errors etc during a development cycle.

Describe the solution you'd like
TEMPORAL_DEBUG env variable is already in use to assist with debugging (e.g. timeouts) and it could be reused to handle all exception as non-retryable by default.

There is some discussion here as well that might provide more context:
https://temporalio.slack.com/archives/CTT84KXK9/p1621341005008500

[vitarb]

Hey @mobiletoly, TEMPORAL_DEBUG is intended to be used to adjust certain timeouts so that when you stop in the debugger you don't affect workflow execution. Your proposal goes slightly against this idea as it would alter workflow behavior by changing how it handles the errors. I don't like this, as it could make certain tests pass/fail with or without the flag.