Restructured the reading of the high order grids for the FEM solver #8263

Job	Run time
Build SU2 (BaseMPI)	13m 6s
Build SU2 (ReverseMPI)	14m 40s
Build SU2 (asan) (BaseNoMPI-asan)	15m 41s
Build SU2 (ForwardMPI)	11m 34s
Build SU2 (tsan) (BaseOMP-tsan)	11m 58s
Build SU2 (asan) (ReverseNoMPI-asan)	44m 50s
Build SU2 (BaseNoMPI)	8m 32s
Build SU2 (tsan) (ReverseOMP-tsan)	27m 52s
Build SU2 (ReverseNoMPI)	12m 22s
Build SU2 (ForwardNoMPI)	9m 36s
Build SU2 (BaseOMP)	7m 39s
Build SU2 (ReverseOMP)	15m 10s
Build SU2 (ForwardOMP)	11m 16s
Unit Tests (test_driver)	1m 26s
Regression Tests (vandv.py)	3m 8s
Unit Tests (test_driver_AD)	1m 30s
Regression Tests (tutorials.py)	6m 27s
Unit Tests (test_driver_DD)	1m 41s
Regression Tests (parallel_regression.py)	14m 18s
Regression Tests (parallel_regression_AD.py)	9m 25s
Regression Tests (serial_regression.py)	16m 29s
Regression Tests (serial_regression_AD.py)	4m 54s
Regression Tests (hybrid_regression.py)	11m 34s
Regression Tests (hybrid_regression_AD.py)	4m 28s
Thread Sanitizer Tests (hybrid_regression.py)	26m 23s
Thread Sanitizer Tests (hybrid_regression_AD.py)	11m 57s
Address Sanitizer Tests (serial_regression.py)	15m 2s
Address Sanitizer Tests (serial_regression_AD.py)	6m 2s
	5h 39m 0s

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