fix: code improvements and cleanup

[shanpriyan]

1. Added cleanup for setTimeout in useEffect.
2. Removed the useEffect which will be triggered based on the removeId state which will further call the removeToast and invoked the removeToast directly inside the setTimeout.
3. Code improvements

   - if (!toastList) return null;
   - if (toastList && !toastList.length) return null;
   + if (!toastList?.length) return null;

   will return null for both falsy values(null,undefined) and empty array [ ]

[shanpriyan]

@mittalchirag