Move status counters to separate table, count replies (#8104)

* Move status counters to separate table, count replies

* Migration to remove old counter columns from statuses table

* Fix schema file

app/models/status_stat.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+# == Schema Information
+#
+# Table name: status_stats
+#
+#  id               :bigint(8)        not null, primary key
+#  status_id        :bigint(8)        not null
+#  replies_count    :bigint(8)        default(0), not null
+#  reblogs_count    :bigint(8)        default(0), not null
+#  favourites_count :bigint(8)        default(0), not null
+#  created_at       :datetime         not null
+#  updated_at       :datetime         not null
+#
+
+class StatusStat < ApplicationRecord
+  belongs_to :status, inverse_of: :status_stat
+end