fix missing SinglePhE_ResponseInPhE_expo2Gaus.dat

[vuillaut]

This PR fixes #1253 by:

• creating a function to get resource data from lstchain
• setting the path to None by default in the config and looking for the default file path in this case

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[morcuended]

pkg_resources is deprecated in favor of importlib.resources

[codecov]

Codecov Report

Attention: Patch coverage is 96.00000% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 73.13%. Comparing base (53dff7e) to head (8cb517a).
Report is 1 commits behind head on main.

❗ Current head 8cb517a differs from pull request most recent head 57a41d5

Please upload reports for the commit 57a41d5 to get more accurate results.

Files	Patch %	Lines
lstchain/visualization/bokeh.py	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1254      +/-   ##
==========================================
+ Coverage   73.11%   73.13%   +0.02%     
==========================================
  Files         134      134              
  Lines       14058    14058              
==========================================
+ Hits        10278    10282       +4     
+ Misses       3780     3776       -4     

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[morcuended]

thanks @vuillaut looks, good to me. I just left a comment

[vuillaut]

Thanks for the review @morcuended
Sorry I made a last-minute change to make sure the default file is indeed used in the tests. Could you review again please?