Convert Modmail to use `createReactionRow` from `redis.js`

Current Behaviour

Modmails are currently directly forwarded from the interactionCreate handler in index.js. It should instead make use of createReactionRow to avoid having custom logic in interactionCreate and so restart-safe interactions work the same as other functions.

Tasks

Things to Do

• Remove custom logic forwarding modmail interactions from index.js
• Use createReactionRow whenever buttons change to update redis so buttons can be forwarded
• Update module.exports.interactionHandler in modmail.js to work with the data sent by handleReactionRow