Operator splitting, adaptive time stepping, and other fixes for mixing layer and bubbles #967

Job	Run time
Georgia Tech \| Phoenix (NVHPC) (cpu)	27m 0s
Github \| Docker	4m 29s
Georgia Tech \| Phoenix (NVHPC) (gpu)	10m 52s
Github (ubuntu, mpi, debug, true)	8m 41s
Github (ubuntu, mpi, debug, false)	5m 33s
Github (ubuntu, mpi, no-debug, true)	9m 58s
Github (ubuntu, mpi, no-debug, false)	5m 14s
Github (ubuntu, no-mpi, debug, true)	6m 37s
Github (ubuntu, no-mpi, debug, false)	3m 12s
Github (ubuntu, no-mpi, no-debug, true)	7m 57s
Github (ubuntu, no-mpi, no-debug, false)	3m 32s
Github (macos, mpi, debug, false)	25m 49s
Github (macos, mpi, no-debug, false)	20m 47s
Github (macos, no-mpi, debug, false)	5m 26s
Github (macos, no-mpi, no-debug, false)	6m 21s
	2h 31m 28s

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