More options for init macro

Added some optional arguments to the init macro.
Only one macro call can be active in a crate because of conflicting implementations.

• default:
  flutter_logger::flutter_logger_init!();
• sepcify level
  flutter_logger::flutter_logger_init!(LeveFilter::Trace);
• sepcify name
  flutter_logger::flutter_logger_init!(logger_init);
• sepcify both
  flutter_logger::flutter_logger_init!(info_logger, LevelFilter::Info);

Support flutter_rust_bridge 2

• Changed setup to support flutter_rust_bridge 2
• macro for easy initialization