[TD-3192] <feature>: support childtable limit and offset.

make insert.json back to early version.

src/kit/taosdemo/insert.json

 {
-	"filetype": "insert",
-	"cfgdir": "/etc/taos",
-	"host": "127.0.0.1",
-	"port": 6030,
-	"user": "root",
-	"password": "taosdata",
-	"thread_count": 4,
-	"thread_count_create_tbl": 4,
-	"result_file": "./insert_res.txt",
+    "filetype": "insert",
+    "cfgdir": "/etc/taos",
+    "host": "127.0.0.1",
+    "port": 6030,
+    "user": "root",
+    "password": "taosdata",
+    "thread_count": 4,
+    "thread_count_create_tbl": 4,
+    "result_file": "./insert_res.txt",
     "confirm_parameter_prompt": "no",
     "insert_interval": 0,
     "num_of_records_per_req": 100,
     "max_sql_len": 1024000,
-	"databases": [{
-		"dbinfo": {
-			"name": "db",
-			"drop": "yes",
-			"replica": 1,
-			"days": 10,
-			"cache": 16,
-			"blocks": 8,
-			"precision": "ms",
-			"keep": 365,
-			"minRows": 100,
-			"maxRows": 4096,
-			"comp":2,
-			"walLevel":1,
-			"cachelast":0,
-			"quorum":1,
-			"fsync":3000,
-			"update": 0
-		},
-		"super_tables": [{
-			"name": "stb",
+    "databases": [{
+        "dbinfo": {
+            "name": "db",
+            "drop": "yes",
+            "replica": 1,
+            "days": 10,
+            "cache": 16,
+            "blocks": 8,
+            "precision": "ms",
+            "keep": 365,
+            "minRows": 100,
+            "maxRows": 4096,
+            "comp":2,
+            "walLevel":1,
+            "cachelast":0,
+            "quorum":1,
+            "fsync":3000,
+            "update": 0
+        },
+        "super_tables": [{
+            "name": "stb",
             "child_table_exists":"no",
-			"childtable_count": 100,
-			"childtable_prefix": "stb_",
-			"auto_create_table": "no",
-			"data_source": "rand",
-			"insert_mode": "taosc",
-            "childtable_limit": 33,
-            "childtable_offset": 33,
-			"insert_rows": 1000,
-			"multi_thread_write_one_tbl": "no",
-			"number_of_tbl_in_one_sql": 0,
-			"rows_per_tbl": 100,
-			"max_sql_len": 1024000,
-			"disorder_ratio": 0,
-			"disorder_range": 1000,
-			"timestamp_step": 1,
-			"start_timestamp": "2020-10-01 00:00:00.000",
-			"sample_format": "csv",
-			"sample_file": "./sample.csv",
-			"tags_file": "",
-			"columns": [{"type": "INT"}, {"type": "DOUBLE", "count":10}, {"type": "BINARY", "len": 16, "count":3}, {"type": "BINARY", "len": 32, "count":6}],
-			"tags": [{"type": "TINYINT", "count":2}, {"type": "BINARY", "len": 16, "count":5}]
-		}]
-	}]
+            "childtable_count": 10000,
+            "childtable_prefix": "stb_",
+            "auto_create_table": "no",
+            "data_source": "rand",
+            "insert_mode": "taosc",
+            "insert_rows": 100000,
+            "multi_thread_write_one_tbl": "no",
+            "number_of_tbl_in_one_sql": 0,
+            "rows_per_tbl": 100,
+            "max_sql_len": 1024000,
+            "disorder_ratio": 0,
+            "disorder_range": 1000,
+            "timestamp_step": 1,
+            "start_timestamp": "2020-10-01 00:00:00.000",
+            "sample_format": "csv",
+            "sample_file": "./sample.csv",
+            "tags_file": "",
+            "columns": [{"type": "INT"}, {"type": "DOUBLE", "count":10}, {"type": "BINARY", "len": 16, "count":3}, {"type": "BINARY", "len": 32, "count":6}],
+            "tags": [{"type": "TINYINT", "count":2}, {"type": "BINARY", "len": 16, "count":5}]
+        }]
+    }]
 }