refactor: move from io/ioutil to io and os package (cosmos#10341)

## Description

The `io/ioutil` package has been deprecated in Go 1.16 (See https://golang.org/doc/go1.16#ioutil). Since cosmos-sdk has upgraded to Go 1.17 (cosmos#9987), this PR replaces the existing `io/ioutil` functions with their new definitions in `io` and `os` packages.

---

### Author Checklist

*All items are required. Please add a note to the item if the item is not applicable and
please add links to any relevant follow up issues.*

I have...

- [x] included the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] added `!` to the type prefix if API or client breaking change
- [x] targeted the correct branch (see [PR Targeting](https://github.com/cosmos/cosmos-sdk/blob/master/CONTRIBUTING.md#pr-targeting))
- [ ] provided a link to the relevant issue or specification
- [x] followed the guidelines for [building modules](https://github.com/cosmos/cosmos-sdk/blob/master/docs/building-modules)
- [ ] included the necessary unit and integration [tests](https://github.com/cosmos/cosmos-sdk/blob/master/CONTRIBUTING.md#testing)
- [x] added a changelog entry to `CHANGELOG.md`
- [ ] included comments for [documenting Go code](https://blog.golang.org/godoc)
- [ ] updated the relevant documentation or specification
- [x] reviewed "Files changed" and left comments if necessary
- [x] confirmed all CI checks have passed

### Reviewers Checklist

*All items are required. Please add a note if the item is not applicable and please add
your handle next to the items reviewed if you only reviewed selected items.*

I have...

- [ ] confirmed the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] confirmed `!` in the type prefix if API or client breaking change
- [ ] confirmed all author checklist items have been addressed 
- [ ] reviewed state machine logic
- [ ] reviewed API design and naming
- [ ] reviewed documentation is accurate
- [ ] reviewed tests and test coverage
- [ ] manually tested (if applicable)

state.go

@@ -4,8 +4,8 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"math/rand"
+	"os"
 	"time"
 
 	tmjson "github.com/tendermint/tendermint/libs/json"
@@ -55,7 +55,7 @@ func AppStateFn(cdc codec.JSONCodec, simManager *module.SimulationManager) simty
 
 		case config.ParamsFile != "":
 			appParams := make(simtypes.AppParams)
-			bz, err := ioutil.ReadFile(config.ParamsFile)
+			bz, err := os.ReadFile(config.ParamsFile)
 			if err != nil {
 				panic(err)
 			}
@@ -194,7 +194,7 @@ func AppStateRandomizedFn(
 // AppStateFromGenesisFileFn util function to generate the genesis AppState
 // from a genesis.json file.
 func AppStateFromGenesisFileFn(r io.Reader, cdc codec.JSONCodec, genesisFile string) (tmtypes.GenesisDoc, []simtypes.Account) {
-	bytes, err := ioutil.ReadFile(genesisFile)
+	bytes, err := os.ReadFile(genesisFile)
 	if err != nil {
 		panic(err)
 	}

utils.go

@@ -3,7 +3,7 @@ package simapp
 import (
 	"encoding/json"
 	"fmt"
-	"io/ioutil"
+	"os"
 
 	"github.com/tendermint/tendermint/libs/log"
 	dbm "github.com/tendermint/tm-db"
@@ -34,7 +34,7 @@ func SetupSimulation(dirPrefix, dbName string) (simtypes.Config, dbm.DB, string,
 		logger = log.NewNopLogger()
 	}
 
-	dir, err := ioutil.TempDir("", dirPrefix)
+	dir, err := os.MkdirTemp("", dirPrefix)
 	if err != nil {
 		return simtypes.Config{}, nil, "", nil, false, err
 	}
@@ -56,7 +56,7 @@ func SimulationOperations(app App, cdc codec.JSONCodec, config simtypes.Config)
 	}
 
 	if config.ParamsFile != "" {
-		bz, err := ioutil.ReadFile(config.ParamsFile)
+		bz, err := os.ReadFile(config.ParamsFile)
 		if err != nil {
 			panic(err)
 		}
@@ -84,7 +84,7 @@ func CheckExportSimulation(
 			return err
 		}
 
-		if err := ioutil.WriteFile(config.ExportStatePath, []byte(exported.AppState), 0600); err != nil {
+		if err := os.WriteFile(config.ExportStatePath, []byte(exported.AppState), 0600); err != nil {
 			return err
 		}
 	}
@@ -96,7 +96,7 @@ func CheckExportSimulation(
 			return err
 		}
 
-		if err := ioutil.WriteFile(config.ExportParamsPath, paramsBz, 0600); err != nil {
+		if err := os.WriteFile(config.ExportParamsPath, paramsBz, 0600); err != nil {
 			return err
 		}
 	}