[PJRT C API] Plumb plugin attributes from plugin to JAX python.

Also add a method for the plugin to return an xla_version plugin attribute.

Currently jaxlib pins a TPU/GPU backend, and uses `xla_extension_version` for backend version. As we want to stop pinning TPU/GPU backend and allow pip install different backend separately, we need this `xla_version` for features that are not capture by PJRT C API version. `xla_extension_version` will still be used for API changes such as xla_client.py, or any XLA changes in jaxlib that are not part of plugins.

PiperOrigin-RevId: 621672421

Author: Jieying Luo

jax/_src/xla_bridge.py

@@ -1065,6 +1065,18 @@ def backend_pjrt_c_api_version(platform=None) -> tuple[int, int] | None:
   return None
 
 
+def backend_xla_version(platform=None) -> int | None:
+  """Returns the XLA version of the backend.
+
+  Returns None if the backend does not use PJRT C API or does not have
+  xla_version in the plugin attributes. This methon can be used to skip features
+  that are not available before certain xla_version if the backend is a
+  plugin and uses xla_version.
+  """
+  backend = get_backend(platform)
+  return getattr(backend, "xla_version", None)
+
+
 @lru_cache
 def local_devices(process_index: int | None = None,
                   backend: str | xla_client.Client | None = None,