refactor bmi adapters into their own library #1631

Job	Run time
test_bmi_cpp (ubuntu-latest)	2m 38s
test_mpi_remote_nexus (ubuntu-latest)	1m 38s
test_bmi_cpp (macos-latest)	6m 0s
test_pet (ubuntu-latest)	2m 36s
test_pet (macos-latest)	4m 35s
test_unit (ubuntu-latest)	5m 17s
test_bmi_fortran (ubuntu-latest)	4m 44s
test_unit (macos-latest)	5m 10s
test_bmi_c (ubuntu-latest)	3m 29s
test_bmi_fortran (macos-latest)	4m 21s
test_bmi_c (macos-latest)	5m 23s
test_bmi_multi (ubuntu-latest)	4m 53s
test_bmi_python (ubuntu-latest)	7m 5s
test_bmi_multi (macos-latest)	6m 22s
test_bmi_python (macos-latest)	10m 36s
	1h 14m 47s

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