Use magicast for astro add

[bluwy]

Changes

fix #11836

Use magicast to simplify our current code and reduce the dependency (particularly @babel/generator and @babel/traverse). The generated code is slightly difference where magicast uses recast that injects new lines and trailing commas in some places. I think it's negligable though

Before:

After:

Testing

Ran astro add manually with different setups.

Docs

n/a. internal change.

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[matthewp]

Should we do this against next instead? astro add is a feature we almost never have to do maintenance on. Glad to reduce the footprint, but not sure doing so in a minor is a good call. If we do it in 5.0 we'll have months to fix bugs this might cause.

[bluwy]

I did another pass and fix some edge cases where they're adding an integration that is already setup. I think it should be fine in the next minor, or even a patch though since the problem magicast solves is well-scoped. I did some tests locally and it's working fine for a lot of happy paths and edge cases. One thing I realize is that before astro add is executed, we also load and validate the astro config, so we know that at least we're dealing with a well-formed config.

I think bugs could happen for sure, but I don't think it would be too hard to solve. The worst case is that users have to manually update the config themselves.

[matthewp]

talked it over and @bluwy feels confident

[bluwy]

If anything happens, feel free to revert it 😅 (But I'll try to look into it too if it's not urgent)