Fixes louvain on projected fragment when v label is not 0

[sighingnow]

What do these changes do?

With projected fragment, 0 may not be in the range of Vertices()/InnerVertices thus cannot be used as the index of vertex arrays.

Related issue number

Fixes #2446

[codecov-commenter]

Codecov Report

Merging #2462 (08f221f) into main (6b1b6cf) will increase coverage by 33.28%.
The diff coverage is 100.00%.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #2462       +/-   ##
===========================================
+ Coverage   39.93%   73.22%   +33.28%     
===========================================
  Files          88       88               
  Lines        9771     9769        -2     
===========================================
+ Hits         3902     7153     +3251     
+ Misses       5869     2616     -3253     

Impacted Files	Coverage Δ
python/graphscope/tests/conftest.py	86.39% <100.00%> (+38.86%)	⬆️
python/graphscope/tests/unittest/test_app.py	96.31% <100.00%> (+96.31%)	⬆️
python/graphscope/framework/dag.py	83.67% <0.00%> (+3.06%)	⬆️
python/graphscope/client/utils.py	86.66% <0.00%> (+3.63%)	⬆️
python/graphscope/analytical/app/java_app.py	28.93% <0.00%> (+4.56%)	⬆️
python/graphscope/client/rpc.py	84.32% <0.00%> (+10.44%)	⬆️
python/graphscope/framework/operation.py	87.67% <0.00%> (+10.95%)	⬆️
python/graphscope/client/session.py	77.38% <0.00%> (+11.58%)	⬆️
python/graphscope/framework/graph_schema.py	64.84% <0.00%> (+12.10%)	⬆️
python/graphscope/analytical/app/bfs.py	100.00% <0.00%> (+12.50%)	⬆️
... and 39 more

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