Remove Inline output mode. Refactor output_mode to `header_only` switch.

docs/source/api/generation.rst

docs/source/usage/config_and_cli.md

docs/source/usage/project_integration.md

integration/test_sycl_buffer.py

src/pystencilssfg/__init__.py

src/pystencilssfg/cmake/modules/PystencilsSfg.cmake

src/pystencilssfg/config.py

src/pystencilssfg/generator.py

tests/generator/test_config.py

tests/generator_scripts/README.md

tests/generator_scripts/index.yaml

tests/generator_scripts/source/SyclKernels.py

tests/generator_scripts/test_generator_scripts.py

tests/integration/cmake_project/CMakeLists.txt

tests/integration/test_cli.py