vid not ASCII/printable in dump tools when it's int-typed

[wey-gu]

(root@nebula) [test]> show create tag test_tag
+------------+-----------------------------------+
| Tag        | Create Tag                        |
+------------+-----------------------------------+
| "test_tag" | "CREATE TAG `test_tag` (          |
|            |  `name` string NULL               |
|            | ) ttl_duration = 0, ttl_col = """ |
+------------+-----------------------------------+

(root@nebula) [test]> INSERT VERTEX test_tag (name) VALUES 13:("n3"), 14:("n4");
Execution succeeded (time spent 2825/7967 us)

Thu, 22 Jul 2021 15:05:01 CST

(root@nebula) [test]> INSERT VERTEX test_tag (name) VALUES 1312:("n312"), 1412:("n412");
Execution succeeded (time spent 1816/15255 us)

sh-4.2# ./db_dump -space_name=test -db_path=/data/storage/nebula/ -meta_server=metad0:9559 -mode=scan -limit=0
===========================PARAMS============================
mode: scan
meta server: metad0:9559
space name: test
path: /data/storage/nebula/
parts:
vids:
tags:
edges:
limit: 0
===========================PARAMS============================

===========================STATISTICS============================
COUNT: 0
VERTEX COUNT: 0
EDGE COUNT: 0
TAG STATISTICS:
EDGE STATISTICS:
============================STATISTICS===========================
Time cost: 124 us

sh-4.2# ./db_dump -space_name=test -db_path=/data/storage/nebula/ -meta_server=metad0:9559 -mode=scan -limit=0
===========================PARAMS============================
mode: scan
meta server: metad0:9559
space name: test
path: /data/storage/nebula/
parts:
vids:
tags:
edges:
limit: 0
===========================PARAMS============================

[vertex] key: 3, , test_tag value: "n4",
[vertex] key: 3, �, test_tag value: "n412",
===========================STATISTICS============================
COUNT: 2
VERTEX COUNT: 2
EDGE COUNT: 0
TAG STATISTICS:
	test_tag : 2
EDGE STATISTICS:
============================STATISTICS===========================
Time cost: 156 us

sh-4.2# ./db_dump -space_name=test -db_path=/data/storage/nebula/ -meta_server=metad0:9559 -mode=scan -limit=0
===========================PARAMS============================
mode: scan
meta server: metad0:9559
space name: test
path: /data/storage/nebula/
parts:
vids:
tags:
edges:
limit: 0
===========================PARAMS============================

[vertex] key: 3, , test_tag value: "n4",         #<--------------------------------------------------
[vertex] key: 3, �, test_tag value: "n412",  #<--------------------------------------------------
===========================STATISTICS============================
COUNT: 2
VERTEX COUNT: 2
EDGE COUNT: 0
TAG STATISTICS:
	test_tag : 2
EDGE STATISTICS:
============================STATISTICS===========================
Time cost: 149 us

context: https://discuss.nebula-graph.com.cn/t/topic/4960