Include memory grouping in the key `MBG`. Fix #1370

[mariodruiz]

This PR fixes #1370.

The new key MBG is created for arguments that are connected to multiple banks.

[codecov-commenter]

Codecov Report

Merging #1372 (21ee322) into image_v2.8 (47cb817) will decrease coverage by 0.07%. The diff coverage is 0.00%.

@@              Coverage Diff               @@
##           image_v2.8    #1372      +/-   ##
==============================================
- Coverage       46.48%   46.40%   -0.08%     
==============================================
  Files              28       28              
  Lines            4963     4971       +8     
  Branches          972      974       +2     
==============================================
  Hits             2307     2307              
- Misses           2599     2607       +8     
  Partials           57       57              

Impacted Files	Coverage Δ
pynq/pl_server/xclbin_parser.py	0.00% <0.00%> (ø)

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[mariodruiz]

xclbinutil source code for the connectivity section is define here https://github.com/Xilinx/XRT/blob/master/src/runtime_src/tools/xclbinutil/SectionConnectivity.cxx and here https://github.com/Xilinx/XRT/blob/master/src/runtime_src/tools/xclbinutil/XclBinUtilities.cxx