Utilise `PetscSection` to constrain essential boundary conditions #9165

Job	Run time
pytest-ubuntu-py311-gcc11-cxxnoomp-base	16m 30s
pytest-ubuntu-py312-gcc12-cxxomp-base	16m 31s
pytest-ubuntu-py310-gcc14-omp-base	16m 30s
pytest-ubuntu-py310-gcc14-omp-adjoint	16m 30s
pytest-ubuntu-py310-gcc9-omp-base	16m 31s
pytest-ubuntu-py312-gcc13-omp-base	16m 30s
pytest-ubuntu-py313-gcc14-omp-adjoint	16m 32s
pytest-ubuntu-py312-gcc13-omp-adjoint	16m 31s
pytest-docker-py310-gcc-omp-arm64-adjoint	16m 29s
pytest-docker-py310-icx-omp-base	16m 32s
pytest-ubuntu-py311-gcc10-noomp-base	16m 31s
pytest-osx-py312-clang-omp-base	16m 34s
pytest-ubuntu-py310-gcc9-omp-adjoint	16m 30s
pytest-docker-py310-icx-omp-adjoint	16m 32s
pytest-ubuntu-py313-gcc14-omp-base	16m 32s
pytest-ubuntu-py311-gcc10-noomp-adjoint	16m 31s
pytest-docker-py310-gcc-omp-base	16m 31s
pytest-docker-py310-gcc-omp-arm64-base	16m 29s
pytest-docker-py310-gcc-omp-adjoint	16m 32s
pytest-ubuntu-py312-gcc12-cxxomp-adjoint	16m 31s
pytest-ubuntu-py311-gcc11-cxxnoomp-adjoint	16m 31s
	5h 46m 50s

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