Rpc: enable getConfirmedBlocks and getConfirmedBlocksWithLimit to return confirmed (not yet finalized) data (#16161)

* Add commitment config capabilities

* Use rpc limit if no end_slot provided

* Limit to actually finalized blocks

* Support confirmed blocks in getConfirmedBlocks and getConfirmedBlocksWithLimit

* Update docs

* Add client plumbing

* Rename config enum

client/src/rpc_config.rs

@@ -2,7 +2,7 @@ use {
     crate::rpc_filter::RpcFilterType,
     solana_account_decoder::{UiAccountEncoding, UiDataSliceConfig},
     solana_sdk::{
-        clock::Epoch,
+        clock::{Epoch, Slot},
         commitment_config::{CommitmentConfig, CommitmentLevel},
     },
     solana_transaction_status::{TransactionDetails, UiTransactionEncoding},
@@ -175,3 +175,19 @@ impl EncodingConfig for RpcConfirmedTransactionConfig {
         }
     }
 }
+
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+#[serde(untagged)]
+pub enum RpcConfirmedBlocksConfig {
+    EndSlotOnly(Option<Slot>),
+    CommitmentOnly(Option<CommitmentConfig>),
+}
+
+impl RpcConfirmedBlocksConfig {
+    pub fn unzip(&self) -> (Option<Slot>, Option<CommitmentConfig>) {
+        match &self {
+            RpcConfirmedBlocksConfig::EndSlotOnly(end_slot) => (*end_slot, None),
+            RpcConfirmedBlocksConfig::CommitmentOnly(commitment) => (None, *commitment),
+        }
+    }
+}