1-tuple: fix copy assignment of tuple containing refs #1407

Job	Run time
perftests (gcc-8, release)	1m 31s
perftests (gcc-9, release)	1m 30s
perftests (gcc-10, release)	1m 43s
perftests (gcc-11, release)	1m 40s
perftests (gcc-12, debug)	2m 7s
perftests (gcc-12, release)	1m 47s
perftests (gcc-13, debug)	2m 11s
perftests (gcc-13, release)	1m 38s
perftests (clang-11, debug)	1m 49s
perftests (clang-11, release)	1m 54s
perftests (clang-12, debug)	1m 58s
perftests (clang-12, release)	1m 53s
perftests (clang-13, release)	1m 55s
perftests (clang-14, release)	2m 8s
perftests (clang-15, debug)	1m 56s
perftests (clang-15, release)	1m 57s
perftests (clang-16, debug)	1m 50s
perftests (clang-16, release)	1m 57s
perftests (clang-14-cuda-11, debug)	5m 56s
perftests (clang-14-cuda-11, release)	5m 6s
perftests (gcc-10-cuda-11.8, debug)	5m 51s
perftests (gcc-10-cuda-11.8, release)	5m 16s
perftests (gcc-11-cuda-12.0, debug)	5m 45s
perftests (gcc-11-cuda-12.0, release)	5m 11s
perftests (gcc-12-cuda-12.3, debug)	5m 58s
perftests (gcc-12-cuda-12.3, release)	5m 14s
perftests (gcc-12-cuda-12.4, debug)	5m 39s
perftests (gcc-12-cuda-12.4, release)	5m 10s
perftests (base-rocm-6.2.2, debug)	4m 53s
perftests (base-rocm-6.2.2, release)	4m 14s
perftests (gcc-10-hpx, release)	3m 27s
perftests (nvhpc-23.3, debug)	8m 36s
perftests (nvhpc-23.3, release)	12m 48s
perftests (nvhpc-23.9, debug)	9m 32s
perftests (nvhpc-23.9, release)	10m 17s
	2h 22m 17s

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