[telemetry] - Rename benchmark_rerun_options to trace_rerun_options.

Since these rerun options are intended to be used for tracing, makes sense to rename + this makes the names consistent with the dashboard.

BUG=

Review URL: https://codereview.chromium.org/946553004

Cr-Commit-Position: refs/heads/master@{#317408}

tools/telemetry/telemetry/results/chart_json_output_formatter.py

@@ -54,7 +54,7 @@ def _ResultsAsChartDict(benchmark_metadata, page_specific_values,
     'format_version': '0.1',
     'benchmark_name': benchmark_metadata.name,
     'benchmark_description': benchmark_metadata.description,
-    'benchmark_rerun_options': benchmark_metadata.rerun_options,
+    'trace_rerun_options': benchmark_metadata.rerun_options,
     'charts': charts,
   }