[MPM] Output process for tracking material point element/condition

[ncrescenzio]

📝 Description

This PR introduces two new output processes (MPMPointOuputProcess and MPMMultiplePointsOutputProcess)) which enable writing data stored in material point (element/condition) variables to file. This feature thus allows users to monitor the evolution of specific material points during the simulation.

The user provides:

• The coordinates of one or multiple target points
• A search tolerance
• The desired output time interval
• The material point variables to be printed

For each specified point, the process:

• Uses the new C++ utility BruteForceMaterialPointLocator to search for the material point closest to the given coordinates.
• Ensures the located material point lies within the user-defined tolerance.
• Writes the selected material point variable values to file at the requested time intervals.

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🆕 Changelog

• New c++ utility BruteForceMaterialPointLocator for finding the material point element/condition closest to a given point by a specified tolerance value.
  • c++ unit test for the new utilitty in test_material_point_locator.cpp
  • python unit test for the new utility in test_material_point_locator.py
  • benchmark (based on google benchmarks) added in Kratos/applications/MPMApplication/benchmarks/brute_force_material_point_locator_benchmark.cpp
• Python output processes:
  • MPMPointOuputProcess: output process for writing data from a material point to a file.
  • MPMMultiplePointsOutputProcess: output process for writing data from several material points to different files.
  • python test in test_mpm_point_output_process.py
• Documentation for the python processes added in Kratos/docs/pages/Applications/MPM_Application/Output_Processes