[vitis++] enable multi-kernel instantiation

[JeffMY05]

1. Related materials

• see example code:
  https://github.com/Xilinx/Vitis_Accel_Examples/blob/f72dff9eea45a76e9ee0713774589624e2b52c9f/sys_opt/slr_assign/Makefile#L89

• Vitis doc, page 323
  ug1393-vitis-application-acceleration.pdf
  https://www.xilinx.com/cgi-bin/docs/rdoc?v=2020.1;d=ug1399-vitis-hls.pdf

• host code modification
  https://xilinx.github.io/Vitis_Accel_Examples/master/html/mult_compute_units.html

• host side for xrt:
  https://pynq.readthedocs.io/en/v2.5.1/pynq_alveo.html

• host side for soc:
  https://pynq.readthedocs.io/en/v2.1/pynq_libraries.html

2. Sub tasks

• needs memory bank partition
• adding new decorator in pylog
• task partition apply ? independent testing
• extend sysgen commands to file-level script