[batch-inserts] Toy for generating batch insert events (dagster-io#20592

)

## Summary & Motivation

Toy definitions for generating larged numbers of batch insert events
from a single-run backfill.

## How I Tested These Changes

Manual execution locally.

python_modules/dagster-test/dagster_test/toys/many_partitions_ranged_backfill.py

@@ -0,0 +1,37 @@
+"""An asset with a large number of partitions (hourly over 1 years = 8760 partitions) and a
+single-run backfill policy. When backfilled, will generate a large number of `store_event` or
+`store_event_batch` calls, depending on if batching is enabled. Use a DummyIOManager to avoid
+unnecessary writes.
+"""
+
+from dagster import (
+    AssetExecutionContext,
+    BackfillPolicy,
+    Definitions,
+    HourlyPartitionsDefinition,
+    IOManager,
+    asset,
+)
+
+partitions_def = HourlyPartitionsDefinition(
+    start_date="2023-01-01-00:00", end_date="2024-01-01-00:00"
+)
+
+
+@asset(partitions_def=partitions_def, backfill_policy=BackfillPolicy.single_run())
+def foo(context: AssetExecutionContext):
+    return {k: 1 for k in context.partition_keys}
+
+
+class DummyIOManager(IOManager):
+    def load_input(self, context, obj):
+        return 1
+
+    def handle_output(self, context, obj):
+        pass
+
+
+defs = Definitions(
+    assets=[foo],
+    resources={"io_manager": DummyIOManager()},
+)