feature(planner): Common tree structure formatter for plan display

[leiysky]

I hereby agree to the terms of the CLA available at: https://databend.rs/dev/policies/cla/

Summary

Introduce a common formatting mechanism for tree stucture, so we can exploit it to imlement EXPLAIN and so on.

A indent format is implemented, here's an example:

PhysicalHashJoin: build keys: [plus(col1, 123)], probe keys: [col2]
    Filter: [true]
        PhysicalScan: catalog.database.table
    PhysicalScan: catalog.database.table

Changelog

• New Feature

Related Issues

Close #5491

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1 Ignored Deployment

Name	Status	Preview	Updated
databend	⬜️ Ignored (Inspect)		May 23, 2022 at 3:13AM (UTC)

[mergify]

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[BohuTANG]

It would be better to add a stateless test for the new explain.

[leiysky]

It would be better to add a stateless test for the new explain.

EXPLAIN isn't involved in this PR. @xudong963 will support it later.