Feature Enhancement: Add visualize_parallel_embeddings Functionality

[AndyZzzZzzZzz]

This PR adds the visualize_parallel_embeddings function, enabling users to visualize parallel embeddings on a D-Wave processor graph with distinct colors for different embeddings.

Additional Details

• Includes an associated test script: test_visualize_parallel_embeddings.
• Complements the functionality introduced in PR #257 on minorminer, providing visualization support for the new parallel_embeddings feature and its demo

[codecov]

Codecov Report

Attention: Patch coverage is 58.33333% with 25 lines in your changes missing coverage. Please review.

Project coverage is 74.61%. Comparing base (7d8aa45) to head (86dc29a).

Files with missing lines	Patch %	Lines
dwave_networkx/drawing/draw_parallel_embeddings.py	57.62%	25 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #247      +/-   ##
==========================================
- Coverage   75.05%   74.61%   -0.45%     
==========================================
  Files          31       32       +1     
  Lines        2213     2273      +60     
==========================================
+ Hits         1661     1696      +35     
- Misses        552      577      +25     

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