Enable support for additional getblock RPC use cases without impacting the method's performance where possible - Option 4

[natalieesk]

Context

This is an implementation of Option 4 from #8390

Tech notes

Option 4

Keep the existing verbosity levels and allow users to, instead of providing a verbosity level, provide a query with exact fields they're interested in on a per-request basis by replacing Zebra's getblock method's verbosity argument type with an enum:

Example

pub trait Rpc {
    fn get_block(&self, hash_or_height: String, query: BlockQuery) -> BoxFuture<Result<GetBlock>>;
    ..
}

#[derive(Debug, Eq, PartialEq, Hash, serde::Deserialize)]
enum BlockField {
    Hash,
    Height,
    Time,
    Confirmations,
    AuthDataRoot,
    MerkleRoot,
    ..
}

#[derive(serde::Deserialize)]
#[serde(untagged)]
enum BlockQuery {
    #[serde(alias = "0")]
    Raw,
    #[serde(alias = "1")]
    Json,
    #[serde(alias = "2")]
    Verbose,
    Fields(HashSet<BlockField>),
}

And replace the zebra_state::Request::BlockHeader(HashOrHeight) variant with a Request::BlockQuery(BlockQuery) variant, and its response variant, BlockHeader(Option<Arc<block::Header>>), with:

Example

enum BlockQueryTx {
    Full(zebra_chain::Transaction),
    Id(transaction::Hash),
}

enum Response {
    BlockQuery {
        // optional version of every field on Header, could add nested options for sapling/orchard tree fields too
        version: Option<u32>,
        previous_block_hash: Option<Hash>,
        merkle_root: Option<merkle::Root>,
        ..
        transactions: Vec<zebra_chain::Transaction>
    }
}

This has the added benefit of allowing for requesting specific block data from the state service without adding new state requests going forward, instead of expecting just a particular Response variant, it would expect the BlockQuery variant with the requested combination of fields being Some.