Make the ObjectCode class lazy load modules

[keenan-simpson]

Currently this is executed at construction time:

if isinstance(module, str):
 # TODO: this option is only taken by the new library APIs, but we have
 # a bug that we can't easily support it just yet (NVIDIA/cuda-python#73).
 if jit_options is not None:
 raise ValueError
 module = module.encode()
 self._handle = handle_return(self._loader["file"](module))
 else:
 assert isinstance(module, bytes)
 if jit_options is None:
 jit_options = {}
 if backend == "new":
 args = (
 module,
 list(jit_options.keys()),
 list(jit_options.values()),
 len(jit_options),
 # TODO: support library options
 [],
 [],
 0,
 )
 else: # "old" backend
 args = (module, len(jit_options), list(jit_options.keys()), list(jit_options.values()))
 self._handle = handle_return(self._loader["data"](*args))

This should happen in a lazy_load method. Certain uses of the ObjectCode object don't require the module to be loaded, such as linking ptx or ltoir code objects together.