Add dpgui entry point and dp gui CLI

[njzjz]

See deepmodeling/dpgui#270 for details.

[codecov]

Codecov Report

Attention: 7 lines in your changes are missing coverage. Please review.

Comparison is base (da100dc) 75.35% compared to head (bf5d6c3) 75.37%.

Additional details and impacted files

@@            Coverage Diff             @@
##            devel    #2904      +/-   ##
==========================================
+ Coverage   75.35%   75.37%   +0.01%     
==========================================
  Files         244      245       +1     
  Lines       24622    24635      +13     
  Branches     1581     1581              
==========================================
+ Hits        18555    18568      +13     
  Misses       5137     5137              
  Partials      930      930              

Files	Coverage Δ
deepmd/entrypoints/__init__.py	100.00% <100.00%> (ø)
deepmd_cli/main.py	98.03% <100.00%> (+0.05%)	⬆️
deepmd/entrypoints/main.py	73.33% <0.00%> (-3.42%)	⬇️
deepmd/entrypoints/gui.py	28.57% <28.57%> (ø)

... and 6 files with indirect coverage changes

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