feat: staking config (#10988)

## Description

staking config to remove DefaultPowerReduction global. 

I want to see if this would be accepted as its easier to document and show users how to do this. 



---

### Author Checklist

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please add links to any relevant follow up issues.*

I have...

- [ ] 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
- [ ] 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
- [ ] 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)
- [ ] added a changelog entry to `CHANGELOG.md`
- [ ] included comments for [documenting Go code](https://blog.golang.org/godoc)
- [ ] updated the relevant documentation or specification
- [ ] reviewed "Files changed" and left comments if necessary
- [ ] confirmed all CI checks have passed

### Reviewers Checklist

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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)

x/staking/simulation/common_test.go

@@ -1,11 +0,0 @@
-package simulation_test
-
-import (
-	"math/big"
-
-	sdk "github.com/cosmos/cosmos-sdk/types"
-)
-
-func init() {
-	sdk.DefaultPowerReduction = sdk.NewIntFromBigInt(new(big.Int).Exp(big.NewInt(10), big.NewInt(18), nil))
-}

x/staking/simulation/operations_test.go

@@ -256,7 +256,6 @@ func TestSimulateMsgBeginRedelegate(t *testing.T) {
 
 // returns context and an app with updated mint keeper
 func createTestApp(t *testing.T, isCheckTx bool, r *rand.Rand, n int) (*simapp.SimApp, sdk.Context, []simtypes.Account) {
-	sdk.DefaultPowerReduction = sdk.NewIntFromBigInt(new(big.Int).Exp(big.NewInt(10), big.NewInt(18), nil))
 
 	accounts := simtypes.RandomAccounts(r, n)
 	// create validator set with single validator
@@ -281,6 +280,7 @@ func createTestApp(t *testing.T, isCheckTx bool, r *rand.Rand, n int) (*simapp.S
 	app.MintKeeper.SetParams(ctx, minttypes.DefaultParams())
 	app.MintKeeper.SetMinter(ctx, minttypes.DefaultInitialMinter())
 
+	app.StakingKeeper.Config.PowerReduction = sdk.NewIntFromBigInt(new(big.Int).Exp(big.NewInt(10), big.NewInt(18), nil))
 	initAmt := app.StakingKeeper.TokensFromConsensusPower(ctx, 200)
 	initCoins := sdk.NewCoins(sdk.NewCoin(sdk.DefaultBondDenom, initAmt))