feat: Vertical transverse isotropic (VTI) solvers: Improve current one ("Fletcher" + add density) + Add other solver ("Zhang") #9278

Job	Run time
semantic_pull_request	4s
is_not_draft_pull_request	5s
are_submodules_in_sync	10s
baseline_log	3s
if_not_unassigned_pull_request	1s
code_coverage / build_test_deploy	9s
Check code style / build_test_deploy	1m 25s
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 11s
Ubuntu (20.04, gcc 9.4.0, open-mpi 4.0.3) / build_test_deploy	6m 9s
Ubuntu (22.04, clang 15.0.7, open-mpi 4.1.2) / build_test_deploy	3m 56s
Ubuntu (22.04, gcc 11.4.0, open-mpi 4.1.2) / build_test_deploy	6m 55s
Ubuntu (22.04, gcc 12.3.0, open-mpi 4.1.2) / build_test_deploy	5m 42s
Ubuntu debug (20.04, gcc 10.5.0, open-mpi 4.0.3) - github codespaces / build_test_deploy	12m 10s
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	13m 28s
Rockylinux CUDA (8, clang 17.0.6, cuda 12.5.1) / build_test_deploy	13m 27s
Rockylinux CUDA (8, gcc 8.5, cuda 12.5.1) / build_test_deploy	52s
Ubuntu CUDA (20.04, clang 10.0.0 + gcc 9.4.0, open-mpi 4.0.3, cuda-11.8.89) / build_test_deploy	12m 41s
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	5m 13s
run_integrated_tests	0s
check_that_all_jobs_succeeded	1s
	1h 29m 47s

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