feat: Vertical transverse isotropic (VTI) solvers: Improve current one ("Fletcher" + add density) + Add other solver ("Zhang") #9281

Job	Run time
semantic_pull_request	3s
is_not_draft_pull_request	2s
if_not_unassigned_pull_request	3s
are_submodules_in_sync	10s
baseline_log	4s
code_coverage / build_test_deploy	5s
Check code style / build_test_deploy	1m 24s
Check documentation / build_test_deploy	1m 5s
Ubuntu (20.04, gcc 10.5.0, open-mpi 4.0.3) - github codespaces / build_test_deploy	6m 13s
Ubuntu (20.04, gcc 9.4.0, open-mpi 4.0.3) / build_test_deploy	5m 44s
Ubuntu (22.04, clang 15.0.7, open-mpi 4.1.2) / build_test_deploy	4m 40s
Ubuntu (22.04, gcc 11.4.0, open-mpi 4.1.2) / build_test_deploy	6m 18s
Ubuntu (22.04, gcc 12.3.0, open-mpi 4.1.2) / build_test_deploy	5m 54s
Ubuntu debug (20.04, gcc 10.5.0, open-mpi 4.0.3) - github codespaces / build_test_deploy	12m 9s
Pangea 3 (AlmaLinux 8.8, gcc 9.4.0, open-mpi 4.1.2, cuda 11.5.0, openblas 0.3.10) / build_test_deploy	39m 49s
Rockylinux CUDA (8, clang 17.0.6, cuda 12.5.1) / build_test_deploy	14m 2s
Rockylinux CUDA (8, gcc 8.5, cuda 12.5.1) / build_test_deploy	53s
Ubuntu CUDA (20.04, clang 10.0.0 + gcc 9.4.0, open-mpi 4.0.3, cuda-11.8.89) / build_test_deploy	10m 10s
Ubuntu CUDA debug (20.04, clang 10.0.0 + gcc 9.4.0, open-mpi 4.0.3, cuda-11.8.89) / build_test_deploy	4m 34s
run_integrated_tests / build_test_deploy	47m 12s
check_that_all_jobs_succeeded	1s
	2h 40m 35s

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