Migrate fragments to use blob rendering

[andrew-johnson-4]

Blobs are infinitely better than fragments due to Type safety and better performance etc.

TODO:

• Blob calling convention (hello-world.lm)
• replace html blob rendering function with this new calling convention
• replace x86 code rendering fragments with this new calling convention

This should be about 2000 lines of code eliminated.

[andrew-johnson-4]

Blob "unused" values end up as the important ones. Type checking doesn't need to change, but codegen gets more interesting.

[andrew-johnson-4]

Blob codegen is just a different calling convention, similar to fragments ans still built on top of the fragment data structure.