clear-stack: switch workflow to matrix; + no-warning when json #13

Job	Run time
test-clear-stack (loop, u8)	1s
compile-clear-stack (loop, u8)	59s
test-clear-stack (loop, u16)	1s
compile-clear-stack (loop, u16)	1m 0s
test-clear-stack (loop, u32)	1s
compile-clear-stack (loop, u32)	59s
test-clear-stack (loop, u64)	1s
compile-clear-stack (loop, u64)	1m 0s
test-clear-stack (loop, u128)	2m 3s
compile-clear-stack (loop, u128)	58s
test-clear-stack (loop, u256)	1s
compile-clear-stack (loop, u256)	59s
compile-clear-stack (loopSCT, u8)	59s
test-clear-stack (loopSCT, u8)	1s
test-clear-stack (loopSCT, u16)	1s
compile-clear-stack (loopSCT, u16)	59s
test-clear-stack (loopSCT, u32)	1s
compile-clear-stack (loopSCT, u32)	58s
test-clear-stack (loopSCT, u64)	1s
compile-clear-stack (loopSCT, u64)	59s
test-clear-stack (loopSCT, u128)	1s
compile-clear-stack (loopSCT, u128)	58s
test-clear-stack (loopSCT, u256)	1s
compile-clear-stack (loopSCT, u256)	58s
test-clear-stack (unrolled, u8)	1s
test-clear-stack (unrolled, u16)	1s
compile-clear-stack (unrolled, u8)	1m 6s
test-clear-stack (unrolled, u32)	1s
compile-clear-stack (unrolled, u16)	1m 3s
test-clear-stack (unrolled, u64)	1s
compile-clear-stack (unrolled, u32)	1m 0s
test-clear-stack (unrolled, u128)	1s
compile-clear-stack (unrolled, u64)	1m 1s
compile-clear-stack (unrolled, u128)	1m 0s
test-clear-stack (unrolled, u256)	1s
compile-clear-stack (unrolled, u256)	1m 4s
	20m 20s

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