Add LG19A4_BOARD prototype to openpiton

[LOCKEDGATE]

This PR adds the prototype of LG19A4_BOARD to openpiton. The FPGA of this development board is Xilinx's xcvu19p. The website of the development board is as follows: (https://www.tangoic.com/home). When using it for the first time, you need to first source env.sh, then source ./piton/ariane_build_tools.sh. For subsequent use, you only need to source env.sh. For other usage tutorials, please refer to the official openpiton repository.