feat: refactor message actions

[ghost]

• actions are in messages rather than in embeds
• actions have custom info set by a bot to distinguish different actions in the same message
• buttons do not have data attached - the action's info is used instead
• text input can have a default value
• document that users cannot add actions to messages, only bots
• document that servers must verify that the user is sending somewhat valid data to the bot
• remove ActionPayload; it is redundant, the only thing that is being sent is a bytes data for all options anyway