feat(coderd): add inbox notifications endpoints (#16889)

This PR is part of the inbox notifications topic, and rely on previous
PRs merged - it adds :

- Endpoints to : 
  - WS : watch new inbox notifications
  - REST : list inbox notifications
  - REST : update the read status of a notification

Also, this PR acts as a follow-up PR from previous work and : 

- fix DB query issues
- fix DBMem logic to match DB

coderd/database/queries.sql.go

@@ -4310,8 +4310,8 @@ func (q *sqlQuerier) CountUnreadInboxNotificationsByUserID(ctx context.Context,
 const getFilteredInboxNotificationsByUserID = `-- name: GetFilteredInboxNotificationsByUserID :many
 SELECT id, user_id, template_id, targets, title, content, icon, actions, read_at, created_at FROM inbox_notifications WHERE
 	user_id = $1 AND
-	template_id = ANY($2::UUID[]) AND
-	targets @> COALESCE($3, ARRAY[]::UUID[]) AND
+	($2::UUID[] IS NULL OR template_id = ANY($2::UUID[])) AND
+	($3::UUID[] IS NULL OR targets @> $3::UUID[]) AND
 	($4::inbox_notification_read_status = 'all' OR ($4::inbox_notification_read_status = 'unread' AND read_at IS NULL) OR ($4::inbox_notification_read_status = 'read' AND read_at IS NOT NULL)) AND
 	($5::TIMESTAMPTZ = '0001-01-01 00:00:00Z' OR created_at < $5::TIMESTAMPTZ)
 	ORDER BY created_at DESC