updates point search for sources and receivers (to be more similar to Cartesian version); adds backward compatibility for Berkeley STF

[danielpeter]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 88.19672% with 36 lines in your changes missing coverage. Please review.

Project coverage is 35.59%. Comparing base (e4e2d68) to head (63a2709).
Report is 5 commits behind head on devel.

Files with missing lines	Patch %	Lines
src/specfem3D/locate_sources.f90	80.13%	29 Missing ⚠️
src/specfem3D/locate_point.f90	95.77%	6 Missing ⚠️
src/specfem3D/setup_sources_receivers.f90	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##            devel     #852      +/-   ##
==========================================
+ Coverage   35.56%   35.59%   +0.03%     
==========================================
  Files         284      284              
  Lines       67693    67727      +34     
==========================================
+ Hits        24076    24110      +34     
  Misses      43617    43617              

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