[BHE/benchmark] add a closed loop network model for the BHE array benchmark

Tests/Data/Parabolic/T/3D_3BHEs_array/3bhes_1U.prj

...s/Data/Parabolic/T/3D_3BHEs_array/bcs_tespy_closedloop.py

...s/Data/Parabolic/T/3D_3BHEs_array/pre/3bhes_closedloop.py

...Es_array/pre/tespy_nw_closedloop/components/char_line.csv

...array/pre/tespy_nw_closedloop/components/cycle_closer.csv

.../tespy_nw_closedloop/components/heat_exchanger_simple.csv

..._3BHEs_array/pre/tespy_nw_closedloop/components/merge.csv

...D_3BHEs_array/pre/tespy_nw_closedloop/components/pump.csv

...HEs_array/pre/tespy_nw_closedloop/components/splitter.csv

.../T/3D_3BHEs_array/pre/tespy_nw_closedloop/connections.csv

...lic/T/3D_3BHEs_array/pre/tespy_nw_closedloop/network.json

...tent/docs/benchmarks/heat-transport-bhe/3D_3BHEs_array.md

...ort-bhe/3D_3BHEs_array_figures/BHE_network_closedloop.png

...D_3BHEs_array_figures/Heat_extraction_rate_closedloop.png

..._3BHEs_array_figures/Inflow_temperature_and_flow_rate.png