Added bipolar membrane unit model and costing #8968

Job	Run time
Check code is formatted (Black)	22s
macOS setup (EXPERIMENTAL) (3.9)	58m 55s
Test notebooks (py3.9/linux)	5m 22s
Code linting (pylint)	4m 22s
Test notebooks (py3.9/win64)	9m 53s
Tests (py3.9/linux)	55m 17s
pytest (user mode) (py3.9/linux)	37m 37s
Test notebooks (py3.11/linux)	5m 10s
Tests (py3.9/win64)	1h 14m 18s
pytest (user mode) (py3.9/win64)	38m 50s
Test notebooks (py3.11/win64)	16m 53s
Tests (py3.10/linux)	48m 27s
pytest (user mode) (py3.11/linux)	28m 26s
Tests (py3.10/win64)	1h 27m 30s
pytest (user mode) (py3.11/win64)	43m 21s
Tests (py3.11/linux)	48m 5s
Tests (py3.11/win64)	1h 31m 20s
Upload coverage report (Codecov)	9s
	10h 54m 17s

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