feat: new type `MsgToL2` with parsing and hashing #201

Job	Run time
Build starknet-ff features	37s
Build starknet-curve features	20s
Build starknet-crypto-codegen features	33s
Build starknet-crypto features	38s
Build starknet-core features	46s
Build starknet-providers features	1m 12s
Build starknet-signers features	36s
Build starknet-accounts features	1m 54s
Build starknet-contract features	1m 27s
Build starknet-macros features	38s
Build starknet features	1m 35s
	10m 16s

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