ActiveRecord::Result#each to yield regular Hash

Followup: rails#51744
Fix: rails#53081
Closes: rails#53088

While the yielded type wasn't specified and we could always
return the more efficient format, there's too many code out
there that depend on this behavior.

Ultimately, queries done with `exec_query` are rare, as long as
Active Record itself use the more efficient path to instantiate
records, most of the gain is obtained.

activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb

@@ -725,8 +725,6 @@ def table_structure_with_collation(table_name, basic_structure)
             end
 
             basic_structure.map do |column|
-              column = column.to_h
-
               column_name = column["name"]
 
               if collation_hash.has_key? column_name

activerecord/lib/active_record/querying.rb

@@ -86,10 +86,10 @@ def _load_from_sql(result_set, &block) # :nodoc:
 
       message_bus.instrument("instantiation.active_record", payload) do
         if result_set.includes_column?(inheritance_column)
-          result_set.map { |record| instantiate(record, column_types, &block) }
+          result_set.indexed_rows.map { |record| instantiate(record, column_types, &block) }
         else
           # Instantiate a homogeneous set
-          result_set.map { |record| instantiate_instance_of(self, record, column_types, &block) }
+          result_set.indexed_rows.map { |record| instantiate_instance_of(self, record, column_types, &block) }
         end
       end
     end

activerecord/lib/active_record/result.rb

@@ -127,9 +127,9 @@ def length
     # Returns an +Enumerator+ if no block is given.
     def each(&block)
       if block_given?
-        indexed_rows.each(&block)
+        hash_rows.each(&block)
       else
-        indexed_rows.to_enum { @rows.size }
+        hash_rows.to_enum { @rows.size }
       end
     end
 
@@ -191,6 +191,7 @@ def cast_values(type_overrides = {}) # :nodoc:
     def initialize_copy(other)
       @rows = rows.dup
       @column_types = column_types.dup
+      @hash_rows    = nil
     end
 
     def freeze # :nodoc:
@@ -212,6 +213,13 @@ def column_indexes # :nodoc:
       end
     end
 
+    def indexed_rows # :nodoc:
+      @indexed_rows ||= begin
+        columns = column_indexes
+        @rows.map { |row| IndexedRow.new(columns, row) }.freeze
+      end
+    end
+
     private
       def column_type(name, index, type_overrides)
         type_overrides.fetch(name) do
@@ -221,13 +229,6 @@ def column_type(name, index, type_overrides)
         end
       end
 
-      def indexed_rows
-        @indexed_rows ||= begin
-          columns = column_indexes
-          @rows.map { |row| IndexedRow.new(columns, row) }.freeze
-        end
-      end
-
       def hash_rows
         # We use transform_values to rows.
         # This is faster because we avoid any reallocs and avoid hashing entirely.