Function filter

filter(
    program: Program,
    callback: (
        instruction: Instruction,
        index: number,
        program: Program,
    ) => boolean,
): Program
Keeps only the instructions a predicate accepts.
Parameters
- program: Program
  Program to filter.
- callback: (instruction: Instruction, index: number, program: Program) => boolean
  Returns true for instructions to keep.
Returns Program
A new program; the input is left untouched.