Support for transactions v2

[holykol]

description: add support for sending and parsing versioned messages that already exist on devnet

docs: Solana proposal: https://docs.solana.com/proposals/transactions-v2#versioned-transactions Rust SDK reference type: https://docs.rs/solana-sdk/latest/solana_sdk/message/enum.VersionedMessage.html

abstract implementation steps:

1. understand when new message version is encoded (if most upper bit of num_required_signatures is set afaik)
2. parse new message fields
3. serialize new version

backwards compatibility concerns:

• do we keep new version backwards compatible or this is going to be new major version of the library?
• or do we add new types and methods like types.DeserializeVersionedMessage([]byte) (MessageV2, error)?
• current version fails to parse new transactions with confusing error messages. Should old methods just return error when they detect newer transaction versions?

[holykol]

@yihau willing to work on this, if no one else is interested

[yihau]

thank you! I just added a PR for this #86 will merge and release soon. maybe you can take a look and give me some feedback? I'm happy to make this SDK more easy to use.

[yihau]

v1.20.0 has included v0 transaction/message serialize/deserialized. feel free to report any bugs you found!