Handle DELETE with LIMIT in Arel

MySQL supports DELETE with LIMIT and ORDER BY.

https://dev.mysql.com/doc/refman/8.0/en/delete.html

Before:

```
  Post Destroy (1.0ms)  DELETE FROM `posts` WHERE `posts`.`id` IN (SELECT `id` FROM (SELECT `posts`.`id` FROM `posts` WHERE `posts`.`author_id` = ? ORDER BY `posts`.`id` ASC LIMIT ?) __active_record_temp)  [["author_id", 1], ["LIMIT", 1]]
```

After:

```
  Post Destroy (0.4ms)  DELETE FROM `posts` WHERE `posts`.`author_id` = ? ORDER BY `posts`.`id` ASC LIMIT ?  [["author_id", 1], ["LIMIT", 1]]
```

2 files changed, 30 insertions, 26 deletions

diff --git a/activerecord/lib/arel/visitors/mysql.rb b/activerecord/lib/arel/visitors/mysql.rb
index ee75b6bb25..0f7d5aa803 100644
--- a/activerecord/lib/arel/visitors/mysql.rb
+++ b/activerecord/lib/arel/visitors/mysql.rb
@@ -65,6 +65,19 @@ module Arel # :nodoc: all
             collector = inject_join o.values, collector, ", "
           end
 
+          collect_where_for(o, collector)
+        end
+
+        def visit_Arel_Nodes_Concat(o, collector)
+          collector << " CONCAT("
+          visit o.left, collector
+          collector << ", "
+          visit o.right, collector
+          collector << ") "
+          collector
+        end
+
+        def collect_where_for(o, collector)
           unless o.wheres.empty?
             collector << " WHERE "
             collector = inject_join o.wheres, collector, " AND "
@@ -77,15 +90,6 @@ module Arel # :nodoc: all
 
           maybe_visit o.limit, collector
         end
-
-        def visit_Arel_Nodes_Concat(o, collector)
-          collector << " CONCAT("
-          visit o.left, collector
-          collector << ", "
-          visit o.right, collector
-          collector << ") "
-          collector
-        end
     end
   end
 end
diff --git a/activerecord/lib/arel/visitors/to_sql.rb b/activerecord/lib/arel/visitors/to_sql.rb
index 87f8c36f9b..575bfd6e36 100644
--- a/activerecord/lib/arel/visitors/to_sql.rb
+++ b/activerecord/lib/arel/visitors/to_sql.rb
@@ -76,12 +76,8 @@ module Arel # :nodoc: all
         def visit_Arel_Nodes_DeleteStatement(o, collector)
           collector << "DELETE FROM "
           collector = visit o.relation, collector
-          if o.wheres.any?
-            collector << WHERE
-            collector = inject_join o.wheres, collector, AND
-          end
 
-          maybe_visit o.limit, collector
+          collect_where_for(o, collector)
         end
 
         # FIXME: we should probably have a 2-pass visitor for this
@@ -97,12 +93,6 @@ module Arel # :nodoc: all
         end
 
         def visit_Arel_Nodes_UpdateStatement(o, collector)
-          if o.orders.empty? && o.limit.nil?
-            wheres = o.wheres
-          else
-            wheres = [Nodes::In.new(o.key, [build_subselect(o.key, o)])]
-          end
-
           collector << "UPDATE "
           collector = visit o.relation, collector
           unless o.values.empty?
@@ -110,12 +100,7 @@ module Arel # :nodoc: all
             collector = inject_join o.values, collector, ", "
           end
 
-          unless wheres.empty?
-            collector << " WHERE "
-            collector = inject_join wheres, collector, " AND "
-          end
-
-          collector
+          collect_where_for(o, collector)
         end
 
         def visit_Arel_Nodes_InsertStatement(o, collector)
@@ -814,6 +799,21 @@ module Arel # :nodoc: all
           }
         end
 
+        def collect_where_for(o, collector)
+          if o.orders.empty? && o.limit.nil?
+            wheres = o.wheres
+          else
+            wheres = [Nodes::In.new(o.key, [build_subselect(o.key, o)])]
+          end
+
+          unless wheres.empty?
+            collector << " WHERE "
+            collector = inject_join wheres, collector, " AND "
+          end
+
+          collector
+        end
+
         def infix_value(o, collector, value)
           collector = visit o.left, collector
           collector << value