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

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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.

:exclamation: 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 :warning:

Additional details and impacted files

```diff @@ 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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[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?