Allow configuring which types of messages get sent as webhook for Discord

[diademiemi]

Information

This PR partially closes #5155

Details

Proposed feature:
Allow configuring which types of messages get sent as a webhook.

Currently when enabling the webhook feature all player specific messages get sent as a webhook. This may not always be desired since this also includes joining the server, deaths, advancements etc.

Environments tested:

OS: Fedora 36

Java version: 17.0.5

• Most recent Paper version (1.XX.Y, git-Paper-BUILD)
• CraftBukkit/Spigot/Paper 1.12.2
• CraftBukkit 1.8.8
  Don't see how this could differ on other server versions.

Demonstration:

This should send all messages as the normal bot user still, but leave chat messages, afk messages and actions as the player.
(Chat messages use a different code path and can't be configured like this, neither can server messages obviously)

send-types-as-player:
  join: false
  # Leave messages sent when a player leaves the Minecraft server.
  first-join: false
  # Leave messages sent when a player leaves the Minecraft server.
  leave: false
  # Death messages sent when a player dies on the Minecraft server.
  death: false
  # AFK status change messages sent when a player's AFK status changes.
  afk: true
  # Achievement/advancement messages sent when a player is awarded an achievement/advancement.
  advancement: false
  # Action messages sent when a player runs the /me or /action commands.
  action: true

(first-join option is from #5160)
(placeholder in username is from #5159)

[diademiemi]

Hey @pop4959, this PR has been open for 1.5 years now, do you have the chance to look at this and potentially merge it?