This commit refactors the Store interface in State into smaller
interfaces in package store. These interfaces are combined into one
structure called a "Cabinet". The default implementation of those
interfaces have been rewritten in package defaultstore, while the old
no-op implementation stays with the store package.
This commit also omitted several state handlers for user events, as it
is unclear what they are actually structured like.
This commit refactored several structures from package discord to be in
package gateway. Those structures are mostly presence ones, which per
official documentation has a lot more to do with the Gateway API than
the REST API or anything else.
This commit also renamed several global variables to have a more
consistent and obvious name.
As of v8, the user API has had a lot of minor and some major changes,
especially regarding its Ready event API. The most significant change is
the addition of the ReadySupplemental event as well as several changes
to the Ready field itself.
All of these changes above are breaking, and they have already broken
the state package. These breaking changes will be addressed in other
packages by the next commit.