Backport slicing improvements 0.26.x #731

Job	Run time
Prepare	5s
Test - stable toolchain	2m 35s
Check WASM	38s
Docs - stable toolchain (recent)	29s
Test - MSRV	3m 27s
Docs - nightly toolchain (recent)	44s
Lint - nightly toolchain (recent)	37s
Test - nightly toolchain	2m 29s
	11m 4s

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