Sum slice impl #869

Job	Run time
build-prover	8m 52s
kit-specs	1m 7s
internal-tests-prover	11m 6s
integer-mate-specs	3m 12s
internal-tests-stackless-bytecode	3m 19s
token-distribution-specs	1m 38s
scallop-bpl-generation	2m 48s
cetus-bpl-generation	4m 44s
ika-bpl-generation	5m 4s
	41m 50s

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