ENH: optimize speed for surface_from_grid method

[jcrivenaes]

Closes #1262

Main elements

• Refactor some C++ vectors with known length to be of type std::array instead of std::vector. In particular the function that receives the corner coordinates, which has fixed length 24. In a future change, we should consider structs in stead
• Alllow top and base and indexes to be returned in the same call
• Avoid recomputing corner coordinates
• Add OMP pragma for parallel processing (in the first implemention for Linux only)

In a concrete case I have, these changes will in effect change the execution for HC thickness maps fram 4-5 minutes to 10 seconds

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 82.05128% with 7 lines in your changes missing coverage. Please review.

Project coverage is 81.14%. Comparing base (0375fed) to head (bf2744a).
Report is 44 commits behind head on main.

Files with missing lines	Patch %	Lines
src/xtgeo/surface/_regsurf_grid3d.py	79.41%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1261      +/-   ##
==========================================
+ Coverage   80.02%   81.14%   +1.11%     
==========================================
  Files          98       94       -4     
  Lines       13680    12433    -1247     
  Branches     2203     1874     -329     
==========================================
- Hits        10948    10089     -859     
+ Misses       1999     1685     -314     
+ Partials      733      659      -74     

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[mferrera]

Really impressive performance gains. OpenMP is magic