simulator: add case about import data

[nolouch]

What problem does this PR solve?

Add a case about import data. This case used to evaluate the region and leader distribution of a table when importing data.

What is changed and how it works?

simulate import data to different table with different speed.

Check List

Tests

• Unit test
• Manual test (add detailed scripts or steps below)

The output like:

INFO[0060] leader distribute (table2) [store 1]:37.50% [store 2]:5.56% [store 4]:20.83% [store 5]:4.17% [store 6]:4.17% [store 7]:2.78% [store 8]:19.44% [store 9]:5.56% 
INFO[0060] peer distribute (table2) [store 1]:21.46% [store 2]:7.31% [store 4]:20.09% [store 5]:7.76% [store 6]:8.22% [store 7]:6.39% [store 8]:22.37% [store 9]:6.39% 

[nolouch]

PTAL

[disksing]

LGTM.

[nolouch]

/run-unit-test

[nolouch]

PTAL