Add getVoteAccounts RPC method parameter to restrict results to a single vote account (#16859)

(cherry picked from commit 59fc33635a)

Co-authored-by: Michael Vines <mvines@gmail.com>

docs/src/developing/clients/jsonrpc-api.md

@@ -2893,11 +2893,14 @@ Returns the account info and associated stake for all the voting accounts in the
 
 #### Parameters:
 
-- `<object>` - (optional) [Commitment](jsonrpc-api.md#configuring-state-commitment)
+- `<object>` - (optional) Configuration object containing the following field:
+  - (optional) [Commitment](jsonrpc-api.md#configuring-state-commitment)
+  - (optional) `votePubkey: <string>` - Only return results for this validator vote address (base-58 encoded)
 
 #### Results:
 
-The result field will be a JSON object of `current` and `delinquent` accounts, each containing an array of JSON objects with the following sub fields:
+The result field will be a JSON object of `current` and `delinquent` accounts,
+each containing an array of JSON objects with the following sub fields:
 
 - `votePubkey: <string>` - Vote account address, as base-58 encoded string
 - `nodePubkey: <string>` - Validator identity, as base-58 encoded string
@@ -2950,6 +2953,49 @@ Result:
 }
 ```
 
+#### Example: Restrict results to a single validator vote account
+
+Request:
+```bash
+curl http://localhost:8899 -X POST -H "Content-Type: application/json" -d '
+  {
+    "jsonrpc": "2.0",
+    "id": 1,
+    "method": "getVoteAccounts",
+    "params": [
+      {
+        "votePubkey": "3ZT31jkAGhUaw8jsy4bTknwBMP8i4Eueh52By4zXcsVw"
+      }
+    ]
+  }
+'
+```
+
+Result:
+```json
+{
+  "jsonrpc": "2.0",
+  "result": {
+    "current": [
+      {
+        "commission": 0,
+        "epochVoteAccount": true,
+        "epochCredits": [
+          [ 1, 64, 0 ],
+          [ 2, 192, 64 ]
+        ],
+        "nodePubkey": "B97CCUW3AEZFGy6uUg6zUdnNYvnVq5VG8PUtb2HayTDD",
+        "lastVote": 147,
+        "activatedStake": 42,
+        "votePubkey": "3ZT31jkAGhUaw8jsy4bTknwBMP8i4Eueh52By4zXcsVw"
+      }
+    ],
+    "delinquent": []
+  },
+  "id": 1
+}
+```
+
 ### minimumLedgerSlot
 
 Returns the lowest slot that the node has information about in its ledger. This