[Solana] Pass serialized message as raw field

[JaimeToca]

With the latest changes regarding Solana versioned transaction, raw is not a "serialized message" anymore and can't be signed, therefore it can create a bit of confusion as clients need to: 1) Decode raw transaction 2) Extract message 3) Serialized message 4) Sign message

Ideally, clients should receive serialized messages that can directly be signed, so apps can return signatures.

[y3fers0n]

Implemented with https://github.com/trustwallet/trust-web3-provider/pull/522