[mlir][TypeDefGen] Add support for adding builders when generating a TypeDef

This allows for specifying additional get/getChecked methods that should be generated on the type, and acts similarly to how OpBuilders work. TypeBuilders have two additional components though:
* InferredContextParam
  - Bit indicating that the context parameter of a get method is inferred from one of the builder parameters
* checkedBody
  - A code block representing the body of the equivalent getChecked method.

Differential Revision: https://reviews.llvm.org/D94274