[Feature]: Add pre-suspend validation

[zhongkechen]

What would you like?

SDK is currently using thread counting mechanism to determine whether or not the execution can be suspended.

The other SDK (e.g. the typescript one) and the durable backend is using operation status checking mechanism - checking whether or not there is any operation in progress

• Java SDK can implement the similar mechanism on top of thread counting to validate the pending/suspension is valid.
• The cloud test runner can check invocation events to confirm there is no error with unexpected pending events.

Possible Implementation

#275

Is this a breaking change?

No

Does this require an RFC?

No

Additional Context

No response