Utilise `PetscSection` to constrain essential boundary conditions #9175

Job	Run time
pytest-ubuntu-py310-gcc14-omp-base	42m 41s
pytest-ubuntu-py312-gcc12-cxxomp-adjoint	35m 34s
pytest-ubuntu-py312-gcc13-omp-base	51m 41s
pytest-osx-py312-clang-omp-base	32m 3s
pytest-docker-py310-gcc-omp-arm64-adjoint	23m 1s
pytest-ubuntu-py310-gcc9-omp-adjoint	31m 11s
pytest-docker-py310-icx-omp-adjoint	27m 25s
pytest-ubuntu-py310-gcc9-omp-base	42m 57s
pytest-ubuntu-py311-gcc10-noomp-base	38m 10s
pytest-ubuntu-py311-gcc11-cxxnoomp-adjoint	29m 24s
pytest-docker-py310-gcc-omp-arm64-base	30m 14s
pytest-ubuntu-py311-gcc10-noomp-adjoint	21m 30s
pytest-docker-py310-icx-omp-base	30m 16s
pytest-ubuntu-py313-gcc14-omp-base	48m 31s
pytest-docker-py310-gcc-omp-base	36m 32s
pytest-ubuntu-py312-gcc13-omp-adjoint	31m 56s
pytest-ubuntu-py313-gcc14-omp-adjoint	30m 38s
pytest-ubuntu-py310-gcc14-omp-adjoint	30m 7s
pytest-ubuntu-py311-gcc11-cxxnoomp-base	33m 26s
pytest-ubuntu-py312-gcc12-cxxomp-base	56m 18s
pytest-docker-py310-gcc-omp-adjoint	26m 10s
	12h 9m 45s

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