Allow batch sampler to not have a .sampler attribute (#20514) #26586

Job	Run time
build-packages / build-packages (lightning)	19s
build-packages / build-packages (fabric)	19s
build-packages / build-packages (pytorch)	22s
build-packages / merge-artifacts	5s
install-pkg (ubuntu-22.04, fabric, 3.9)	1m 38s
install-pkg (ubuntu-22.04, fabric, 3.11)	1m 40s
install-pkg (ubuntu-22.04, pytorch, 3.9)	1m 48s
install-pkg (ubuntu-22.04, pytorch, 3.11)	1m 43s
install-pkg (ubuntu-22.04, lightning, 3.9)	1m 48s
install-pkg (ubuntu-22.04, lightning, 3.11)	1m 45s
install-pkg (ubuntu-22.04, notset, 3.9)	1m 57s
install-pkg (ubuntu-22.04, notset, 3.11)	1m 56s
install-pkg (macOS-14, fabric, 3.9)	48s
install-pkg (macOS-14, fabric, 3.11)	32s
install-pkg (macOS-14, pytorch, 3.9)	52s
install-pkg (macOS-14, pytorch, 3.11)	33s
install-pkg (macOS-14, lightning, 3.9)	54s
install-pkg (macOS-14, lightning, 3.11)	43s
install-pkg (macOS-14, notset, 3.9)	1m 24s
install-pkg (macOS-14, notset, 3.11)	47s
install-pkg (windows-2022, fabric, 3.9)	1m 54s
install-pkg (windows-2022, fabric, 3.11)	1m 55s
install-pkg (windows-2022, pytorch, 3.9)	2m 25s
install-pkg (windows-2022, pytorch, 3.11)	2m 58s
install-pkg (windows-2022, lightning, 3.9)	1m 49s
install-pkg (windows-2022, lightning, 3.11)	2m 47s
install-pkg (windows-2022, notset, 3.9)	2m 16s
install-pkg (windows-2022, notset, 3.11)	2m 20s
	40m 17s

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