Operator splitting, adaptive time stepping, and other fixes for mixing layer and bubbles #964

Job	Run time
Georgia Tech \| Phoenix (NVHPC) (cpu)	1h 37m 6s
Github (ubuntu, mpi, debug, true)	29m 23s
Georgia Tech \| Phoenix (NVHPC) (gpu)	12m 26s
Github \| Docker	53m 54s
Github (ubuntu, mpi, debug, false)	55m 16s
Github (ubuntu, mpi, no-debug, true)	51m 50s
Github (ubuntu, mpi, no-debug, false)	54m 30s
Github (ubuntu, no-mpi, debug, true)	20m 13s
Github (ubuntu, no-mpi, debug, false)	19m 26s
Github (ubuntu, no-mpi, no-debug, true)	32m 26s
Github (ubuntu, no-mpi, no-debug, false)	18m 22s
Github (macos, mpi, debug, false)	45m 58s
Github (macos, mpi, no-debug, false)	44m 10s
Github (macos, no-mpi, debug, false)	23m 18s
Github (macos, no-mpi, no-debug, false)	24m 57s
	9h 43m 15s

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