Add support for setting line_width on datashader line aggregation

[philippjfr]

Adds support for setting line_width on datashader aggregation operations if datashader version >= 0.14.

Also adds support for rescale_discrete_levels option on shade operation.

[codecov-commenter]

Codecov Report

Merging #5264 (093d330) into master (e3af887) will decrease coverage by 0.00%.
The diff coverage is 80.95%.

@@            Coverage Diff             @@
##           master    #5264      +/-   ##
==========================================
- Coverage   86.75%   86.75%   -0.01%     
==========================================
  Files         298      298              
  Lines       62162    62176      +14     
==========================================
+ Hits        53929    53939      +10     
- Misses       8233     8237       +4     

Impacted Files	Coverage Δ
holoviews/operation/datashader.py	80.00% <80.95%> (-0.11%)	⬇️

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[jlstevens]

Tests are passing so feel free to merge if you think this is ready.

[github-actions]

This pull request has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.