Added some verify actions for checkpoint test plan

[bright-starry-sky]

1, Added restore meta server from checkpoint.
2, Added vertices verify action :

• verify data changed after snapshot created, expected old data after restore.
• verify new vertices inserted after snapshot created, expect that the data doesn't exist.

This plan passed.

[bright-starry-sky]

Depends PR:
vesoft-inc/nebula#2318

[panda-sheep]

Good job！

[panda-sheep]

Why add this field?
Isn't the default position in actions the sequence number?

[panda-sheep]

Can you rebase master?

[CLAassistant]

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