Generic API for Pyro Backends

pyro-api provides a generic, backend-agnostic API for probabilistic programming, allowing users to write code that can be executed with different Pyro backends (e.g., Pyro, NumPyro, Funsor) without modification. It aims to abstract common functionalities like distributions, inference primitives, and parameter management. The current version is 0.1.2, and it maintains a slow release cadence, primarily focusing on stability and compatibility.