Reduce size of generated client

[timsuchanek]

With a schema with 350 models and about 5000 fields, we generate a index.js of about 25mb with 100.000 lines and an index.d.ts of about 27mb with about 500.000 lines.

Just starting a simple script with JavaScript only takes 20s, that's the pure parsing and getting V8 smaller.

On top, the TypeScript compilation of a script importing @prisma/client takes 45s.

We can reduce the JavaScript runtime overhead by lazily generating the api dynamically in runtime.

The TypeScript declarations might be reduced by introducing more generics for types, which users don't import, but take a lot of space.

[timsuchanek]

Done in latest alpha.