implement chillidkg #814

Job	Run time
build	3m 10s
Rustfmt	14s
clippy_check	25s
test (x86_64-unknown-linux-gnu)	4m 1s
test-minimal (secp256kfun)	1m 15s
test-nightly	1m 35s
test (armv7-unknown-linux-gnueabihf)	6m 59s
test-minimal (sigma_fun)	2m 39s
test-minimal (ecdsa_fun)	40s
test-minimal (schnorr_fun)	51s
doc-build	27s
test-alloc (secp256kfun)	1m 5s
test-alloc (sigma_fun)	2m 38s
test-alloc (ecdsa_fun)	40s
test-alloc (schnorr_fun)	1m 8s
	27m 47s

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