fix: allign rpc client with agave

[sonicfromnewyoke]

Problem

RPC client has drifted behind the Agave reference implementation
several response fields added in recent Agave releases are missing
these gaps mean callers cannot access data that Agave validators already return, and some request options available in the Rust client have no Go equivalen

Summary of Changes

resp fields added:

• ApiVersion
• GetClusterNodesResult - TPUForwards, TPUForwardsQUIC, TPUVote, ServeRepair, ClientID; FeatureSet changed to *uint32 to match Option
• TransactionIndex in TransactionSignature
• InflationRewardsCommissionBps in VoteAccountsResult
• NumNonVoteTransactions in GetRecentPerformanceSamplesResult

req options added:

• GetProgramAccountsOpts - WithContext, SortResults
• new GetProgramAccountsWithContext method that returns context (slot/apiVersion) instead of silently discarding it
• GetLargestAccountsOpts struct + GetLargestAccountsWithOpts method with SortResults
• RequestAirdropOpts struct + RequestAirdropWithOpts method with RecentBlockhash

GetInflationRateResult.Epoch: float64 -> uint64
closes #345