fix: update virtualenv building so llamastack- prefix is not added, make notebook experience easier (#1225)

Make sure venv behaves like conda (no prefix is added to image_name) and
`--image-type venv` inside a notebook "just works" without any fiddling

llama_stack/distribution/library_client.py

@@ -41,6 +41,7 @@ from llama_stack.distribution.stack import (
     redact_sensitive_fields,
     replace_env_vars,
 )
+from llama_stack.distribution.utils.exec import in_notebook
 from llama_stack.providers.utils.telemetry.tracing import (
     end_trace,
     setup_logger,
@@ -52,19 +53,6 @@ logger = logging.getLogger(__name__)
 T = TypeVar("T")
 
 
-def in_notebook():
-    try:
-        from IPython import get_ipython
-
-        if "IPKernelApp" not in get_ipython().config:  # pragma: no cover
-            return False
-    except ImportError:
-        return False
-    except AttributeError:
-        return False
-    return True
-
-
 def convert_pydantic_to_json_value(value: Any) -> Any:
     if isinstance(value, Enum):
         return value.value