Do not remove "dead" domains in tootctl accounts cull (#9108)

Leave `tootctl accounts cull` to simply check removed accounts from
live domains, and skip temporarily unavailable domains, while listing
them in the final output for further action.

Add `tootctl domains purge DOMAIN` to be able to purge a domain from
that list manually

lib/mastodon/domains_cli.rb

@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+require_relative '../../config/boot'
+require_relative '../../config/environment'
+require_relative 'cli_helper'
+
+module Mastodon
+  class DomainsCLI < Thor
+    def self.exit_on_failure?
+      true
+    end
+
+    option :dry_run, type: :boolean
+    desc 'purge DOMAIN', 'Remove accounts from a DOMAIN without a trace'
+    long_desc <<-LONG_DESC
+      Remove all accounts from a given DOMAIN without leaving behind any
+      records. Unlike a suspension, if the DOMAIN still exists in the wild,
+      it means the accounts could return if they are resolved again.
+    LONG_DESC
+    def purge(domain)
+      removed = 0
+      dry_run = options[:dry_run] ? ' (DRY RUN)' : ''
+
+      Account.where(domain: domain).find_each do |account|
+        unless options[:dry_run]
+          SuspendAccountService.new.call(account)
+          account.destroy
+        end
+
+        removed += 1
+        say('.', :green, false)
+      end
+
+      DomainBlock.where(domain: domain).destroy_all
+
+      say
+      say("Removed #{removed} accounts#{dry_run}", :green)
+    end
+  end
+end