Add Tree.Edit benchmark

[hackerwins]

Description:

Recently, Yorkie provides Tree for WYSIWYG editors that have a tree-based model. Let's add benchmarks of Tree to track its performance.

Tree specifications:

• https://github.com/yorkie-team/yorkie/blob/main/test/integration/tree_test.go

Similar issues:

• Suggest to add PushPull benchmark test #600
• Do benchmark operations of the document #180
• Find the cause of the linear increase in text benchmark execution time #251

Why:

It is important to track performance when adding new features or methods because Tree is a data structure and sometimes users may load a lot of data to it.

[JOOHOJANG]

It would be nice for a new contributor to do it, but I think I should do it right away because it's related to the work I'm doing right now. Can I take it?

[hackerwins]

@JOOHOJANG Sure, give it a try.