Keep the original CBOR in the transaction witness while deserializing transaction bytes to maintain the same datum hash

[satran004]

• Keep the original CBOR in Transaction / TransactionWitnessSet to avoid incorrect datum hash due to deserialization -> serialization.
• Add an immutable API layer for Transaction, TransactionWitness, PlutusData, etc.
• Add Transaction.of(bytes) and TransactionBody.of(bytes) to get an immutable copy.