Fix breaking changes and bugs before release

[lukellmann]

Some breaking changes were discovered since the last release (e.g. here). This tries to revert those and includes some additional fixes.

• The overload resolution ambiguity reported here was fixed.

• NewsChannelBehavior was missing TopGuildMessageChannelBehavior as a supertype since ThreadParentChannelBehavior is no longer a TopGuildMessageChannelBehavior.

• TextChannelBehavior was missing TopGuildMessageChannelBehavior as a supertype since PrivateThreadParentChannelBehavior is no longer a TopGuildMessageChannelBehavior.

• ThreadParentChannelBehavior was extended to be a CategorizableChannelBehavior (implicating that ThreadParentChannel was also extended to be a CategorizableChannel).

• TextChannelBehavior's startPublicThread and startPrivateThread had an additional reason parameter added, breaking binary compatibility. The reason can be specified in the builder lambda.

• TextChannelBehavior.startPublicThreadWithMessage had the archiveDuration parameter removed, breaking binary compatibility.

• Binary incompatibility in Integration was fixed.

• Missing Optional default values were added in IntegrationData.

• The event type for ForumChannels was changed from UnknownChannel[Create|Update|Delete]Event to ForumChannel[Create|Update|Delete]Event.

• Some optionalities and nullabilities were fixed.

• Integration events now use Integration entities from core instead of DiscordIntegration from common.

• Audit Log Entries from GuildAuditLogEntryCreate events are no longer cached. They aren't queried through cache so putting them there doesn't make sense.

• Wrong SerialName annotation for components was removed.

• Old constructor of StartThreadWithMessageBuilder was reintroduced to preserve binary compatibility.

• StartThreadWithoutMessageBuilder was renamed back to StartThreadBuilder to preserve binary compatibility.

• Forum Tag routes and related declarations were removed because they are not documented in Discord's docs and have odd behavior. See the discussion here for details.

• The serializer of GuildMemberFlags was made internal, it is accessible through GuildMemberFlags.serializer().

• Some minor things were refactored and simplified.

• The asChannel, asChannelOrNull, fetchChannel, fetchChannelOrNull and withStrategy methods were overridden in ForumChannel and ForumChannelBehavior so they have the correct return type.

• The Intents.IntentsBuilder.enableEvent function was updated to add the right intent for ForumChannel events.

• Support for webhooks was moved up from TopGuildMessageChannelBehavior to CategorizableChannelBehavior. This was done because ForumChannels also support webhooks but are not TopGuildMessageChannels. The only concrete Channel type that received webhook support by this change is ForumChannel.

• The Discord prefix was removed from DiscordForumTag and DiscordDefaultReaction. These types are used in core and do not contain any optional fields.

• ForumTagBuilder is no longer a AuditRequestBuilder, its reason was unused. The name property was also made var and public.

• Missing properties of ThreadChannel, ForumChannel and TextChannel were added.

• Message count caching was updated. Updating lastMessageId and message counts was combined into one update operation for MessageCreate and totalMessageSent is no longer decremented on MessageDelete and MessageDeleteBulk, the whole point of it is to not decrement.

• The default value for the builder paremeter of ForumChannelBehavior.startPublicThread was removed. Not having a default empty builder lambda in will nudge users into thinking about what belongs in there. This is needed because you have to provide a message in that lambda to successfully create a forum post.

• Removed ForumThreadModifyBuilder, it was almost the same as ThreadModifyBuilder, just with an additional flags property, which was just copied over to ThreadModifyBuilder instead.
  Having a single builder for both cases is more maintainable and keeps the API simpler.

• StartForumThreadBuilder.message was made non-nullable, as it is always required. StartForumThreadBuilder.createMessage was also renamed to message because a thread is started that just contains a message.

• The builder parameter of ChannelService.startThread was accidentally unused.

The full diff between the last release and this PR can be seen here to verify that the breaking changes were in fact reverted: 0.8.0-M17...5a805cc

[lukellmann]

I want to make sure that the breaking changes were reverted by looking at the full diff in detail. I will tell you if I'm done with that and this PR is ready to merge (however, it is already ready to review).