Upgrade @babel/* to v8

[trevor-scheer]

Upgrades the @babel/* toolchain from v7 to v8 across the monorepo. Supersedes #4372, which bumped only @babel/types and left v8 types running against the v7 parser — Babel 8 packages have to move together.

Bumping to v8 surfaced a pile of dead babel config and dependencies: a root babel.config.js left over from the babel-jest days, plugins that v8 now folds in as always-on stable features, @babel/polyfill, and the tooling that only existed to feed the old config. Packages build with tsc/vite and test on vitest now, so none of it has a live consumer — it's all pruned here.

A couple of things needed real handling rather than a version bump:

• graphql-language-service-server parses source files with @babel/parser, so its BABEL_PLUGINS list and the vue.ts AST types had to adapt to v8's ParserPlugin union and the @babel/types v7/v8 skew that @vue/compiler-sfc bundles.
• babel-plugin-react-compiler runs through @vitejs/plugin-react's own @babel/core@7, which targets Babel 7 AST. Nothing pins @babel/traverse, so the compiler's Babel 7 stack and the monorepo's Babel 8 stack resolve side by side. Pinning @babel/traverse to v8 breaks the compiler.

[changeset-bot]

🦋 Changeset detected

Latest commit: 65a99f6

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
graphql-language-service-server	Patch
graphql-language-service-cli	Patch

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