[Bug] Core throws HeartbeatTimeoutNotSet when activity heartbeats and no heartbeat timeout is configured

[bergundy]

Describe the bug
As described in title, record_activity_heartbeat throws when there's no heartbeat timeout configured.

sdk-core/src/lib.rs

Line 404 in 1ba0450

.ok_or(ActivityHeartbeatError::HeartbeatTimeoutNotSet)?

It would be better to ignore or simply warn in this case since the activity sending heartbeats is decoupled from the workflow that sets its ActivityOptions.

To Reproduce
Schedule an activity without a heartbeat timeout.

[Sushisource]

For posterity: @bergundy As we discussed it makes sense to solve this by re-routing the error on the lang side. Let me know if we need to do anything else here otherwise you can close/move this.

[bergundy]

Agreed, I'll come up with a design for propagating these errors back into the activity.