message: Make parser operate over streams, not paths
diff: use std::error::Error;
  -use std::fs::File;
  -use std::io::BufReader;
  -use std::path::Path;
  use crate::ir_types::Program;
  -pub fn load(bril_file_path: &Path) -> Result<Program, Box<dyn Error>> {
  - let bril_file = File::open(bril_file_path)?;
  - let bril_data = BufReader::new(bril_file);
  - let bril_prog = serde_json::from_reader(bril_data)?;
  +pub fn load(bril_file_stream: Box<dyn std::io::Read>) -> Result<Program, Box<dyn Error>> {
  + let bril_prog = serde_json::from_reader(bril_file_stream)?;
  Ok(bril_prog)
  }
  