feat: provide AST node types with internal types stripped out (alternative)

[dummdidumm]

Alternative to #12967 which moves all nodes into an AST namespace. Sadly, I found out after adjusting the whole codebase that it doesn't work properly because dts-buddy can't handle this properly. Not sure if we should look into it or just go with
#12967 instead (fixed in dts-buddy).

Question remaining is, whether or not we should also expose the type unions, like SvelteNode etc, or just the AST nodes themselves. I lean towards the latter, which would mean I need to tweak this PR a bit. Update: we decided to hide those

Depends on Rich-Harris/dts-buddy#87 and Rich-Harris/dts-buddy#89 being merged and released

closes #12292

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🦋 Changeset detected

Latest commit: e17a930

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[dummdidumm]

Will self-merge once green to not introduce more merge conflicts