[Feature Request] Add workflow API to create independent deterministic pseudo-number sequence

[mjameswh]

Context

• Some Workflow Plugins need to call Math.random() or workflow.uuid4().
• If the workflow code also use these methods, then the plugin and the workflow code both pull values out of the same PRNG sequence.
• That may result in NDEs if a workflow is replayed after adding/removing a Plugin.

Describe the solution you'd like

Add the following to the Workflow API:

1. API to create a distinct deterministic PRNG instance
2. Possibility of generating UUIDs from that distinct PRNG instances (i.e. rather than only from the workflow’s global PRNG).
3. Possibility of activating a given PRNG instance as the “global” one within a given execution scope. This is required to ensure that third-party, non-Temporal libraries used by Temporal plugins don’t disrupt the workflow’s actual PRNG sequence.