Improve get route astar

[joamatab]

improve astar router thanks to @juanferv

#57 (comment)

original astar code was made by @SkandanC

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Codecov Report

Attention: Patch coverage is 20.00000% with 24 lines in your changes are missing coverage. Please review.

Project coverage is 71.74%. Comparing base (0e1b0cf) to head (573f593).

Files	Patch %	Lines
gdsfactory/routing/get_route_astar.py	20.00%	24 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2752      +/-   ##
==========================================
+ Coverage   71.64%   71.74%   +0.09%     
==========================================
  Files         369      369              
  Lines       23892    23858      -34     
  Branches     3889     3882       -7     
==========================================
- Hits        17118    17116       -2     
+ Misses       5652     5620      -32     
  Partials     1122     1122              

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[juanferv]

cool fixing! now it is working even with optical layers. It works in a lot of dificcult scenarios. We want to test it in difficult scenario of a routing