Rpc: introduce get_inflation_reward rpc call (#16278) (#16410)

* feat: introduce get_inflation_reward rpc call

* fix: style suggestions

* fix: more style changes and match how other rpc functions are defined

* feat: get reward for a single epoch

* feat: default to the most recent epoch

* fix: don't factor out get_confirmed_block

* style: introduce from impl for RpcEncodingConfigWrapper

* style: bring commitment into variable

* feat: support multiple pubkeys for get_inflation_reward

* feat: add get_inflation_reward to rpc client

* feat: return rewards in order

* fix: rename pubkeys to addresses

* docs: introduce jsonrpc docs for get_inflation_reward

* style: early return in map (not sure which is more idiomatic)

* fix: call the rpc client function args addresses as well

* fix: style

* fix: filter out only addresses we care about

* style: make this more idiomatic

* fix: change rpc client epoch to optional and include some docs edits

* feat: filter out rent rewards in get_inflation_reward

* feat: add option epoch config param to get_inflation_reward

* feat: rpc client get_inflation_reward takes epoch instead of config and some filter staking and voting rewards

(cherry picked from commit e501fa5f0b)

Co-authored-by: Josh <josh.hundley@gmail.com>

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

@@ -40,6 +40,7 @@ gives a convenient interface for the RPC methods.
 - [getIdentity](jsonrpc-api.md#getidentity)
 - [getInflationGovernor](jsonrpc-api.md#getinflationgovernor)
 - [getInflationRate](jsonrpc-api.md#getinflationrate)
+- [getInflationReward](jsonrpc-api.md#getinflationreward)
 - [getLargestAccounts](jsonrpc-api.md#getlargestaccounts)
 - [getLeaderSchedule](jsonrpc-api.md#getleaderschedule)
 - [getMaxRetransmitSlot](jsonrpc-api.md#getmaxretransmitslot)
@@ -1468,6 +1469,58 @@ Result:
 {"jsonrpc":"2.0","result":{"epoch":100,"foundation":0.001,"total":0.149,"validator":0.148},"id":1}
 ```
 
+### getInflationReward
+
+Returns the inflation reward for a list of addresses for an epoch
+
+#### Parameters:
+- `<array>` - An array of addresses to query, as base-58 encoded strings
+* `<object>` - (optional) Configuration object containing the following optional fields:
+  * (optional) [Commitment](jsonrpc-api.md#configuring-state-commitment)
+  * (optional) `epoch: <u64>` - An epoch for which the reward occurs. If omitted, the previous epoch will be used
+
+#### Results
+
+The result field will be a JSON array with the following fields:
+
+- `epoch: <u64>`, epoch
+- `effective_slot: <u64>`, the slot in which the rewards are effective
+- `amount: <u64>`, reward amount in lamports
+- `post_balance: <u64>`, post balance of the account in lamports
+
+#### Example
+
+Request:
+```bash
+curl http://localhost:8899 -X POST -H "Content-Type: application/json" -d '
+  {
+    "jsonrpc": "2.0",
+    "id": 1,
+    "method": "getInflationReward",
+    "params": [
+       ["6dmNQ5jwLeLk5REvio1JcMshcbvkYMwy26sJ8pbkvStu", "BGsqMegLpV6n6Ve146sSX2dTjUMj3M92HnU8BbNRMhF2"], 2
+    ]
+  }
+'
+```
+
+Response:
+```json
+  {
+    "jsonrpc": "2.0",
+    "result": [
+        {
+            "amount": 2500,
+            "effectiveSlot": 224,
+            "epoch": 2,
+            "postBalance": 499999442500
+        },
+        null
+    ],
+    "id": 1
+  }
+```
+
 ### getLargestAccounts
 
 Returns the 20 largest accounts, by lamport balance (results may be cached up to two hours)