[DOCS] Add stage recompute intro

[zuston]

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• [X] I have searched in the issues and found no similar issues.

Which parts of the documentation do you think need improvement?

Thanks to the efforts of @advancedxy and @yl09099 , the stage recompute has been supported.

We'd better to add more docs to describe this design and effect, and the dedicated article is also necessary for this big feature

Affects Version(s)

master

Improving the documentation

No response

Anything else

No response

Are you willing to submit PR?

• [ ] Yes I am willing to submit a PR!

[zuston]

Do you want to take this? @yl09099

[yl09099]

Do you want to take this? @yl09099

Okay, let me write that down.