[Indexes] Add TxIndex: Transaction index, RPC, and native pruning

[D-Stacks]

TxIndex: Transaction index, RPC, and pruning

Summary
This PR adds a new optional transaction index (TxIndex) that maintains acceptance and inclusion metadata for transactions, exposes get_transaction via RPC when enabled, supports resync from scratch, live updates from consensus notifications (virtual chain, block, and retention root events), and incremental on-the-fly self-pruning behavior tied to consensus retention root changes.

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Activation

• How to enable: Runtime flag --txindex.

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New rpc call: GetTransaction

• newly supported call when the TxIndex is active.
• walk-thorough based on rust structs:
• request:

pub struct GetTransactionRequest {
   // The to-query transaction
   pub transaction_id: RpcTransactionId,
   // weather to include non-accepted transactions into the data.
   // note: if include_unaccepted is false this will only include the data of the transaction that is currently accepted for both transaction as well as inclusion data results, else these will return a vec of all transactions registered by the txindex 
   pub include_unaccepted: bool,
   // the returned verbosity of the RpOptionalTransaction (if any), verbosity mimics GetVirtualChainV2 filtering. 
   // resolved input utxos are supplied on a best effort basis.  
   pub transaction_verbosity: Option<RpcDataVerbosityLevel>,
   // the inclusion data of txs found, 
   pub include_inclusion_data: bool,
   // the current canonical acceptance data found for the transaction (if any)
   pub include_acceptance_data: bool,
   // the confirmation count of the transaction  
   pub include_conf_count: bool,
}

• response:

pub struct GetTransactionResponse {
    pub transaction_data: Option<RpcTransactionData>,
}

• new Rpc structs:

pub struct RpcTransactionData {
    pub transactions: Vec<RpcOptionalTransaction>,
    pub inclusion_data: Vec<RpcTransactionInclusionData>,
    pub acceptance_data: Option<RpcTransactionAcceptanceData>,
    pub conf_count: Option<u64>,
}

pub struct RpcTransactionInclusionData {
    /// The hash of the block that includes the transaction
    pub including_block_hash: RpcHash,
    /// This is the daa score of the block that includes the transaction
    pub including_daa_score: u64,
    /// The index within the block that this transaction occupies
    pub index_within_block: TransactionIndexType,
}

pub struct RpcTransactionAcceptanceData {
    /// The hash of the block that accepted the transaction
    pub accepting_block_hash: RpcHash,
    /// The blue score of the block that accepted the transaction
    pub accepting_blue_score: u64,
    /// The index of the including block within the mergeset of the accepting block
    pub mergeset_index: MergesetIndexType,
}