Java DSL: Predictable task naming when name is not provided

[ricardozanini]

What would you like to be added:
The Java DSL should be able to add predictable names to every task if users pass null or empty strings. For example, a FuncWorkflowBuilder.workflow().tasks(set(Map.of("message", "hello"))) should be named set-1 instead of a random ID as it's today.

Why is this needed:
Predictable and descriptive task names improve debuggability and maintainability, especially for generated workflows. Random IDs make it difficult to track, test, or reason about workflows. Naming as set-1, set-2, etc. aligns with developer expectations and eases project collaboration.