test_page_service_batching: fix non-numeric metrics (#9998)

## Problem

```
2024-12-03T15:42:46.5978335Z + poetry run python /__w/neon/neon/scripts/ingest_perf_test_result.py --ingest /__w/neon/neon/test_runner/perf-report-local
2024-12-03T15:42:49.5325077Z Traceback (most recent call last):
2024-12-03T15:42:49.5325603Z   File "/__w/neon/neon/scripts/ingest_perf_test_result.py", line 165, in <module>
2024-12-03T15:42:49.5326029Z     main()
2024-12-03T15:42:49.5326316Z   File "/__w/neon/neon/scripts/ingest_perf_test_result.py", line 155, in main
2024-12-03T15:42:49.5326739Z     ingested = ingest_perf_test_result(cur, item, recorded_at_timestamp)
2024-12-03T15:42:49.5327488Z                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
2024-12-03T15:42:49.5327914Z   File "/__w/neon/neon/scripts/ingest_perf_test_result.py", line 99, in ingest_perf_test_result
2024-12-03T15:42:49.5328321Z     psycopg2.extras.execute_values(
2024-12-03T15:42:49.5328940Z   File "/github/home/.cache/pypoetry/virtualenvs/non-package-mode-_pxWMzVK-py3.11/lib/python3.11/site-packages/psycopg2/extras.py", line 1299, in execute_values
2024-12-03T15:42:49.5335618Z     cur.execute(b''.join(parts))
2024-12-03T15:42:49.5335967Z psycopg2.errors.InvalidTextRepresentation: invalid input syntax for type numeric: "concurrent-futures"
2024-12-03T15:42:49.5336287Z LINE 57:             'concurrent-futures',
2024-12-03T15:42:49.5336462Z                      ^
```

## Summary of changes
- `test_page_service_batching`: save non-numeric params as `labels`
- Add a runtime check that `metric_value` is NUMERIC

test_runner/fixtures/benchmark_fixture.py

@@ -266,6 +266,16 @@ class NeonBenchmarker:
         name = f"{self.PROPERTY_PREFIX}_{metric_name}"
         if labels is None:
             labels = {}
+
+        # Sometimes mypy can't catch non-numeric values,
+        # so adding a check here
+        try:
+            float(metric_value)
+        except ValueError as e:
+            raise ValueError(
+                f"`metric_value` (`{metric_value}`) must be a NUMERIC-friendly data type"
+            ) from e
+
         self.property_recorder(
             name,
             {

test_runner/performance/pageserver/test_page_service_batching.py

@@ -116,21 +116,18 @@ def test_throughput(
             # name is not a metric, we just use it to identify the test easily in the `test_...[...]`` notation
         }
     )
-    params.update(
-        {
-            f"pipelining_config.{k}": (v, {})
-            for k, v in dataclasses.asdict(pipelining_config).items()
-        }
-    )
+    # For storing configuration as a metric, insert a fake 0 with labels with actual data
+    params.update({"pipelining_config": (0, {"labels": dataclasses.asdict(pipelining_config)})})
 
     log.info("params: %s", params)
 
     for param, (value, kwargs) in params.items():
         zenbenchmark.record(
             param,
-            metric_value=value,
+            metric_value=float(value),
             unit=kwargs.pop("unit", ""),
             report=MetricReport.TEST_PARAM,
+            labels=kwargs.pop("labels", None),
             **kwargs,
         )