Update the scenario result schema for additional fields.

Add startTime and endTime fields in the summary field.

There are other fields such as core_syscall_epoll_ctl and
core_pollset_fd_cache_hits fields in both clientStats
and serverStats are added back since the only way to update
fields inside a record would be using command: `bq update`,
which requires the schema to match the existing BigQuery
table. The startTime and endTime fields are added to summary
field which is a record.

Author: wanlin31

tools/run_tests/performance/scenario_result_schema.json

@@ -180,6 +180,16 @@
         "name": "core_pollset_kick_own_thread",
         "type": "INTEGER"
       },
+      {
+        "mode": "NULLABLE", 
+        "name": "core_syscall_epoll_ctl", 
+        "type": "INTEGER"
+      },
+      {
+        "mode": "NULLABLE", 
+        "name": "core_pollset_fd_cache_hits", 
+        "type": "INTEGER"
+      },
       {
         "mode": "NULLABLE",
         "name": "core_histogram_slow_lookups",
@@ -1012,6 +1022,16 @@
         "name": "core_pollset_kick_own_thread",
         "type": "INTEGER"
       },
+      {
+        "mode": "NULLABLE", 
+        "name": "core_syscall_epoll_ctl", 
+        "type": "INTEGER"
+      },
+      {
+        "mode": "NULLABLE", 
+        "name": "core_pollset_fd_cache_hits", 
+        "type": "INTEGER"
+      },  
       {
         "mode": "NULLABLE",
         "name": "core_histogram_slow_lookups",
@@ -1833,6 +1853,16 @@
         "mode": "NULLABLE",
         "name": "clientQueriesPerCpuSec",
         "type": "FLOAT"
+      },
+      {
+        "mode": "NULLABLE",
+        "name": "startTime",
+        "type": "TIMESTAMP"
+      },
+      {
+        "mode": "NULLABLE",
+        "name": "endTime",
+        "type": "TIMESTAMP"
       }
     ],
     "mode": "NULLABLE",