Provide getGuid() method in java workflow SDK #931

Describe the proposal

As required by documentation "Workflow functions must call deterministic APIs"

https://docs.dapr.io/developing-applications/building-blocks/workflow/workflow-features-concepts/#workflow-functions-must-call-deterministic-apis

// DON'T DO THIS!
DateTime currentTime = DateTime.UtcNow;
Guid newIdentifier = Guid.NewGuid();
string randomString = GetRandomString();

DateTime currentTime = context.CurrentUtcDateTime;
Guid newIdentifier = context.NewGuid();
string randomString = await context.CallActivityAsync<string>("GetRandomString");

Now in java workflow SDK, we don't provide such getGuid() method (yeat context.getCurrentInstant() method is provided) .

We need to improve our java workflow sdk to provide this getGuid() method.

And this getGuid() method is NOT provided by durable task java SDK, so we need to update durable task java SDK first.

This improvement should be included in next release.