controller: add commissioner-side commissioning building blocks #2728

Job	Run time
build_and_test (mbedtls)	1m 7s
build_and_test (openssl)	1m 7s
build_and_test (rustcrypto)	1m 7s
build_and_test (rustcrypto, os)	25s
build_and_test (rustcrypto, alloc)	1m 5s
build_and_test (openssl, os)	1m 7s
build_and_test (openssl, alloc)	1m 7s
build_and_test (mbedtls, os)	1m 8s
build_and_test (mbedtls, alloc)	1m 7s
	9m 20s

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