Feature: Crypto dart library

[balladyna]

The purpose of this branch is to reimplement the SHA-256 and SHA-512 algorithms based on the crypto library. This addition enables secure hashing, which is essential for supporting operations related to Bitcoin, Ethereum and Cosmos, such as generating addresses, validating mnemonics and signing transactions.

List of changes:

• created a_hash.dart, to serve as an abstraction for cryptographic hash functions by managing the conversion of byte input into a digest
• created a_hash_sink.dart, to efficiently process streaming hash input by handling incoming data in chunks, managing buffering and ensuring correct endian formatting
• created digest.dart, to represent the final output of hashing algorithm
• created digest_sink.dart, to ensure that only the first received digest is stored, preventing overwrites
• created a_sha_32bit_sink.dart, sha256.dart and sha256_sink.dart, to initialize the digest state, configure hash computation, define a block size and provide hashing logic for SHA-256
• created a_sha_64bit_sink.dart, sha512.dart and sha512_sink.dart, to initialize the digest state, configure hash computation, define a block size and provide hashing logic for SHA-512