Implement verifier for higher level intermediate representation in codegen ir

Motivation

We want to introduce a pass on the higher level ir of the natrix codegen backend, that validates the semantical correctness of the program. We hope that this will

1. Improve the developer experience as the compiler itself will tell you about an error in the ir and you don't have to figure it out yourself
2. make finding bugs easier. E.g., by running the verifier after each optimization pass, we can validate that the optimization did not leave the program in an undefined state
3. decrease the amount of work a language frontend has to do by itself by providing additional warnings (e.g. for unreachable code, ...) and coupling them with their original source code location

Definition of done

• Check for use before def
• Check for semantically correct types in instructions
• Check for missing terminator
• Check branch args
• Report with source code location
• Add warnings (like unreachable code)
• Check entry basic block exists