Currently the return data has to fit in shared memory, 8MB (Linux, Windows) or 1MB (Apple)
Preparation for streaming is added (to allow unlimited return data, see CMD_CUSTOM_COMMAND_STREAM_RETURN_DATA)
New C-API: b3GetStatusPluginCommandReturnData
PyBullet reports return data if available, in pybullet_executePluginCommand
For the plugin developer:
plugin can provide additional return data for executePluginCommand in the b3PluginContext, during executePluginCommand.
Lifetime of this m_returnData pointer is minimum of next call to the next executePluginCommand or plugin termination.