refactor(transformer): use AstBuilder instance from TraverseCtx

[shulaoda]

closes #6172

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[codspeed-hq]

CodSpeed Performance Report

Merging #6173 will not alter performance

_{Comparing shulaoda:refactor/transformer-transform-ctx (e049c50) with main (f2ac584)}

Summary

✅ 29 untouched benchmarks

[shulaoda]

Could you reopen this PR? 😂 @Dunqing

[Dunqing]

Sorry, I tagged wrong

[overlookmotel]

Thank you so much for doing this.

Apart from the comment above about reverting traverse_mut to how it was, looks great.

Please could make that change and ping me, so I can do a final review and merge it ASAP before we get merge conflicts?

[overlookmotel]

@shulaoda This has merge conflicts and I was worried that if I requested changes, there'd be more merge conflicts again by the time I got to reviewing your changes (probably we are in different time zones, and this PR touches a lot of files in the transformer, which is currently under heavy development).

So I have taken the liberty of rebasing this on latest main, fixing the problem discussed above, and merging it.

Sorry if it feels like I've taken over your work. I just really didn't want to waste your time going back-and-forwards endlessly dealing with merge conflicts. Really appreciate your work on this.