add _enable_polars_execution to proxy executor

Author: TrevorBergeron

packages/bigframes/bigframes/session/proxy_executor.py

@@ -54,14 +54,15 @@ def __init__(
         publisher: bigframes.core.events.Publisher,
         labels: Mapping[str, str] = {},
     ):
+        self._enable_polars_execution = enable_polars_execution
         shared_cache = execution_cache.ExecutionCache()
         self._ibis_executor = bq_caching_executor.BigQueryCachingExecutor(
             bqclient,
             storage_manager,
             bqstoragereadclient,
             loader,
             metrics=metrics,
-            enable_polars_execution=enable_polars_execution,
+            enable_polars_execution=self._enable_polars_execution,
             publisher=publisher,
             labels=labels,
             cache=shared_cache,
@@ -73,7 +74,7 @@ def __init__(
             bqstoragereadclient,
             loader,
             metrics=metrics,
-            enable_polars_execution=enable_polars_execution,
+            enable_polars_execution=self._enable_polars_execution,
             publisher=publisher,
             labels=labels,
             cache=shared_cache,