FEAT-#7459: Add methods to get and set backend. #16332

Job	Run time
execution-filter	5s
python-filter	1s
lint (mypy)	2m 11s
Test API, headers and no-engine mode	2m 14s
lint (flake8)	16s
test-internals	6m 40s
Test BaseOnPython execution, Python 3.9"	6m 50s
test-clean-install-ubuntu	3m 49s
test-asv-benchmarks	19s
test-clean-install-windows	2m 31s
test-ubuntu (engine unidist ${{ matrix.unidist-backend }}, python ${{ matrix.python-version }})	0s
test-ubuntu (engine python, python 3.9, group_1)	6m 44s
test experimental	6m 50s
test-ubuntu (engine native, python 3.9, group_1)	6m 50s
test-ubuntu-sanity (engine ray, python 3.9)	6m 48s
test-windows (engine python, python 3.9, group_1)	6m 32s
test-spreadsheet (engine ray, python 3.9)	2m 11s
test-windows (engine native, python 3.9, group_1)	6m 36s
test-ubuntu-sanity (engine dask, python 3.9)	6m 49s
test-spreadsheet (engine dask, python 3.9)	2m 8s
test-ubuntu-sanity (engine unidist, python 3.9)	6m 48s
test-windows-sanity (engine ray, python 3.9)	6m 33s
test-native-dataframe-interoperability python 3.9)	3m 53s
test-windows-sanity (engine dask, python 3.9)	6m 34s
test-windows-sanity (engine unidist, python 3.9)	6m 32s
merge-coverage-artifacts	2s
upload-coverage	18s
	1h 47m 4s

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