Adds an option to pass node_labels to visualize_graph

[vahanhov]

Addresses #8770

Note that these are used only with graphviz backend.

[codecov]

Codecov Report

Attention: 6 lines in your changes are missing coverage. Please review.

Comparison is base (019c5b3) 89.39% compared to head (fbfb709) 89.39%.
Report is 1 commits behind head on master.

❗ Current head fbfb709 differs from pull request most recent head 6082ef7. Consider uploading reports for the commit 6082ef7 to get more accurate results

Files	Patch %	Lines
torch_geometric/visualization/graph.py	16.66%	5 Missing ⚠️
torch_geometric/explain/explanation.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8816      +/-   ##
==========================================
- Coverage   89.39%   89.39%   -0.01%     
==========================================
  Files         479      479              
  Lines       31146    31134      -12     
==========================================
- Hits        27844    27831      -13     
- Misses       3302     3303       +1     

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