Extract handleAppStateChange in confirmation components into re-usable hook.

Nobody has claimed this yet.

### **Description**

`handleAppStateChange` takes care to cancel current transaction when app is no longer active.

The code includes registering listeners:
```
AppState.addEventListener('change', this.handleAppStateChange);
AppState.removeEventListener('change', this.handleAppStateChange);
```
And functions calls:

https://github.com/MetaMask/metamask-mobile/blob/bdb7f37c90e4fc923881a07fca38d4e77c73a579/app/components/Views/ApproveView/Approve/index.js#L372

https://github.com/MetaMask/metamask-mobile/blob/bdb7f37c90e4fc923881a07fca38d4e77c73a579/app/components/Views/Approval/index.js#L139

This can be extracted to a re-usable hook.

### **Acceptance Criteria**
The functionality to cancel transaction and close modal when app is not working should continue to work as expected on both screens.

### **References**
https://docs.google.com/document/d/19xKY4e07UThOa1jsDQA8pjsNLUBRn39EdUbaFpz3OR0/edit?usp=sharing

Start by comparing app/components/Views/ApproveView/Approve/index.js around the linked handleAppStateChange call with app/components/Views/Approval/index.js around its listener setup. Trace how each screen registers and removes the AppState listener, then verify that both screens still cancel the transaction and close the modal when the app is inactive.

Written by the indexing model from the issue text.