Operator splitting, adaptive time stepping, and other fixes for mixing layer and bubbles #207

Job	Run time
Georgia Tech \| Phoenix (NVHPC) (cpu)	45m 59s
Github (ubuntu, mpi, debug, true)	46m 36s
Georgia Tech \| Phoenix (NVHPC) (gpu)	29m 26s
Github (ubuntu, mpi, debug, false)	1h 2m 21s
Github (ubuntu, mpi, no-debug, true)	59m 1s
Github (ubuntu, mpi, no-debug, false)	59m 15s
Github (ubuntu, no-mpi, debug, true)	22m 20s
Github (ubuntu, no-mpi, debug, false)	17m 23s
Github (ubuntu, no-mpi, no-debug, true)	34m 25s
Github (ubuntu, no-mpi, no-debug, false)	19m 36s
Github (macos, mpi, debug, false)	35m 47s
Github (macos, mpi, no-debug, false)	46m 8s
Github (macos, no-mpi, debug, false)	13m 46s
Github (macos, no-mpi, no-debug, false)	39m 0s
Github \| Docker	58m 18s
	9h 49m 21s

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