[Feature]: convenient methods for UUID/timestamp/random

[zhongkechen]

What would you like?

Create convenient methods in DurableContext to create steps wrapping UUID, timestamp and etc.

• ctx.uuid() - UUID
• ctx.now() - current Instant
• ctx.random() - generate a random number between 0 and 1

Possible Implementation

No response

Is this a breaking change?

No

Does this require an RFC?

No

Additional Context

No response