ParallelExecutor no longer needs std::ref #6952

Job	Run time
spack-centos-stream (GCC11-NoMPI-Debug-Real)	19m 26s
macos (macOS-GCC14-NoMPI-Real)	14m 55s
spack-centos-stream (GCC11-NoMPI-NoOMP-Real)	18m 56s
linux (GCC9-NoMPI-Debug-Real)	16m 40s
spack-centos-stream (GCC11-NoMPI-NoOMP-Complex)	18m 25s
linux (GCC9-NoMPI-NoOMP-Real)	16m 14s
spack-centos-stream (GCC11-NoMPI-Sandbox-Real)	4m 31s
linux (GCC9-NoMPI-NoOMP-Complex)	16m 22s
linux (GCC9-MPI-Sandbox-Real)	3m 47s
linux (GCC9-NoMPI-Sandbox-Complex)	3m 49s
linux (GCC9-MPI-Gcov-Real)	27m 1s
linux (GCC9-MPI-Gcov-Complex)	27m 8s
linux (GCC12-NoMPI-Werror-Real)	19m 40s
linux (GCC12-NoMPI-Werror-Complex)	19m 25s
linux (GCC12-NoMPI-Werror-Real-Mixed)	18m 3s
linux (GCC12-NoMPI-Werror-Complex-Mixed)	18m 39s
linux (Clang14-NoMPI-ASan-Real)	23m 46s
linux (Clang14-NoMPI-ASan-Complex)	23m 14s
linux (Clang14-NoMPI-UBSan-Real)	23m 33s
linux (Clang16-NoMPI-Offload-Real)	21m 36s
linux (Clang16-NoMPI-Offload-Complex)	21m 55s
	6h 17m 5s

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