Bump `crypto-bigint` dependency to v0.7.0-rc.12 #1145

Job	Run time
build (1.85.0, wasm32-unknown-unknown)	25s
build (stable, thumbv7em-none-eabi)	24s
build (1.85.0, thumbv7em-none-eabi)	24s
test (stable)	6m 51s
test (1.85.0)	7m 1s
nightly	1m 2s
build (stable, wasm32-unknown-unknown)	23s
minimal-versions	-1s
	16m 29s

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