Change `write-bytecode' to accept a bytevector.

Change `write-bytecode' to accept a bytevector.

* module/language/assembly/compile-bytecode.scm (write-bytecode):
  Replace the WRITE-BYTE and GET-ADDR parameters with PORT.  New ADDRESS
  and EMIT-OPCODE? parameters.  Callers updated.
  [write-byte, get-addr]: New procedures.
  Adjust to write to PORT.
  (compile-bytecode): Update accordingly.

* test-suite/tests/asm-to-bytecode.test (munge-bytecode): Return a
  bytevector instead of a u8vector.
  (comp-test): Deal with bytevectors.