View sample data for tags & edges

[Sophie-Xie]

Describe the background of the requirement
When customers get a new Nebula Graph and don't know the data details, customers always don't know how to start using our products(Nebula Graph、explorer、studio)

Describe the detail of the requirement
For relational database(mysql):
When we get a new database, we can know it with below:
1.show databases;
2.show tables;
3.desc <table_name> or show create <table_name>;
4.select * from <table_name> limit 10;

For nebula graph:
when we get a new database:
1.show spaces;
2.show tags & show edges;
3.show create {TAG <tag_name> | EDGE <edge_name>};
No match (v:<tag_name>) return v limit 10; (need to create index)

Can we supply a way to view sample data for tags & edges without index? then at least we can get a "vid" for query or any other operations.

Describe the scenarios of the requirement
1.First use of our products，don't know data details, want to understand the data structure quickly.
2.Don't know data details, want to test expand through explorer.(Need VID)

Describe the values of the requirement
General: nebula graph usability
Values for customer: Facilitate customers to better use our products(Nebula Graph,explorer,studio)，make it easier for customers to understand the data structure
Importance of the business project:it's common request

from @Jerry319609l