Build: Ship the default TypeScript .d.ts declaration files, not rollups

[adamziel]

pipeline. This caused the published packages to ship not just their own types but also all the types they import. This creates a lot of noise and also type identity conflicts between packages. This PR removes most of these rollup tasks, leaving only two:

• In the @wp-playground/blueprints package for Types->JSON schema generation
• In the @wp-playground/client package to make it self-contained and dependencyless.

Related to #1577

Testing instructions

Run npm run build and confirm the built packages only export their own types.