get/set command line arguments in SBLaunchInfo

[roccoblues]

This enables us to set cli arguments of the debugged process with set_arguments() and retrieve an iterator over them with arguments().

One unexpected thing I noticed is that target.launch(lauch_info) does not persist the launch info in the target. But this seems to be a "feature" of the C++ API. Eg.

let target = debugger.create_target(executable, None, None, false)?;
let launch_info = SBLaunchInfo::new();
launch_info.set_launch_flags(LaunchFlags::STOP_AT_ENTRY);
target.launch(launch_info)?;

// target.get_launch_info().launch_flags() <-- this is different from above

let target = debugger.create_target(executable, None, None, false)?;
let launch_info = SBLaunchInfo::new();
launch_info.set_launch_flags(LaunchFlags::STOP_AT_ENTRY);
target.set_launch_info(launch_info.clone());
target.launch(launch_info)?;

// target.get_launch_info().launch_flags() <-- now it matches