refactor(tsp1.f90): move code from gwt1.f90 to tsp1.f90 #1339

Job	Run time
Smoke test	4m 48s
Build	2m 56s
Check format	1m 22s
Test gnu fortran (ubuntu-22.04)	23m 50s
Test intel fortran (ubuntu-22.04, intel-classic, 2021.7)	23m 26s
Test gnu fortran (macos-12)	35m 53s
Parallel testing (ubuntu-22.04)	21m 15s
Test intel fortran (macos-12, intel-classic, 2021.7)	41m 18s
Test gnu fortran (windows-2022)	34m 20s
Parallel testing (macos-12)	48m 47s
Test intel fortran (windows-2022, intel-classic, 2021.7)	1h 10m 56s
	5h 8m 51s

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