Operator splitting, adaptive time stepping, and other fixes for mixing layer and bubbles #204

Job	Run time
Github \| Docker	58m 13s
Georgia Tech \| Phoenix (NVHPC) (cpu)	45m 27s
Github (ubuntu, mpi, debug, true)	25m 19s
Georgia Tech \| Phoenix (NVHPC) (gpu)	29m 27s
Github (ubuntu, mpi, debug, false)	1h 5m 26s
Github (ubuntu, mpi, no-debug, true)	57m 9s
Github (ubuntu, mpi, no-debug, false)	58m 45s
Github (ubuntu, no-mpi, debug, true)	19m 28s
Github (ubuntu, no-mpi, debug, false)	20m 4s
Github (ubuntu, no-mpi, no-debug, true)	35m 17s
Github (ubuntu, no-mpi, no-debug, false)	18m 43s
Github (macos, mpi, debug, false)	31m 15s
Github (macos, mpi, no-debug, false)	44m 19s
Github (macos, no-mpi, debug, false)	17m 48s
Github (macos, no-mpi, no-debug, false)	21m 50s
	9h 8m 30s

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