[NT-293] Reset reward scroll view on prepareForReuse

[ifbarrera]

📲 What

Resets the contentOffset of the scroll view in the RewardCell on prepareForReuse to ensure that any new rewards coming into view are scrolled to the top of the reward.

🤔 Why

It's visually confusing to see rewards that have already been scrolled.

🛠 How

Created a view model for RewardCell, and created an input for the RewardCell collection view cell's prepareForReuse function. This triggers the scrollScrollViewToTopoutput which resets the cells scroll view's contentOffset to it's initial point.

👀 See

Trello, screenshots, external resources?

Before 🐛	After 🦋

✅ Acceptance criteria

• Navigate to the rewards screen. Find a reward that is longer than the height of the screen and scroll down to the bottom (vertical scrolling). Then, keep scrolling horizontally. All new rewards coming into the screen should be scrolled to the initial starting point. Scrolling back to the previously-scrolled-down reward should show the reward scrolled to it's starting point.

[cdolm92]

Amazing, this is G2G!! 🛳🛳🛳🛳

✅ACs passed, tested on iPhone 7