Refactor to remove code generation

[kili-ilo]

The current code generation system is less helpful than expected:

• The generated files are all very simple, and could simply be copy/pasted instead of generated.
• The .graphql files require special decorators, which have a limited syntax.
• The versioning strategy (only some command files are versioned, but most are ignored and should be regenerated mid-build) is counterintuitive.
• Adding unique features to commands requires ejecting from code generation.

Therefore, we should:

• Replace all .graphql files with their generated .ts counterparts.
• Remove all code generation scripts & dependencies.

[kili-ilo]

This will remove some warning of backwards-incompatible API changes, so we should also add some automated validation/testing (see #7).