Refactor: Remove sampler dependency on MapData (github issue #168)

[noellehmcheng]

I have made the following changes to remove the Sampler class dependency on MapData class:

1. Moved get_value_from_raster_df and __value_from_raster from MapData to utils.py and renamed them to set_z_values_from_raster_df and value_from_raster
2. Modified Sampler class to take datasets directly instead of the entire MapData object
3. Updated the corresponding code to accommodate these changes

• extract_geology_contacts in project.py
• calculate_fault_orientations in project.py
• summarise_fault_data in project.py
• sample in SamplerDecimator class
• compute in InterpolatedStructure class

Validation
I ran the code in map2loop-notebooks/Example 3- Local Source Data.ipynb and compared the returned result from set_z_values_from_raster_df function inside extract_geology_contacts. The results from the current master branch and the refactored code are the same.