Avoid method call if @transaction_state is not finalized

Method call in Ruby is a bit slow.

This makes attribute access 10% faster by avoiding method call
(`sync_with_transaction_state`).

Before (96cf7e0):

```
Warming up --------------------------------------
             user.id   131.291k i/100ms
          user['id']    91.786k i/100ms
           user.name   151.605k i/100ms
        user['name']    92.664k i/100ms
       user.changed?    17.772k i/100ms
 user.saved_changes?    23.909k i/100ms
Calculating -------------------------------------
             user.id      1.988M (± 7.0%) i/s -      9.978M in   5.051474s
          user['id']      1.155M (± 5.8%) i/s -      5.783M in   5.022672s
           user.name      2.450M (± 4.3%) i/s -     12.280M in   5.021234s
        user['name']      1.263M (± 2.1%) i/s -      6.394M in   5.066638s
       user.changed?    175.070k (±13.3%) i/s -    853.056k in   5.011555s
 user.saved_changes?    259.114k (±11.8%) i/s -      1.267M in   5.001260s
```

After (this change):

```
Warming up --------------------------------------
             user.id   137.625k i/100ms
          user['id']    96.054k i/100ms
           user.name   156.379k i/100ms
        user['name']    94.795k i/100ms
       user.changed?    18.172k i/100ms
 user.saved_changes?    24.337k i/100ms
Calculating -------------------------------------
             user.id      2.201M (± 0.5%) i/s -     11.010M in   5.002955s
          user['id']      1.320M (± 1.0%) i/s -      6.628M in   5.021293s
           user.name      2.677M (± 1.6%) i/s -     13.449M in   5.024399s
        user['name']      1.314M (± 1.8%) i/s -      6.636M in   5.051444s
       user.changed?    190.588k (±11.1%) i/s -    944.944k in   5.065848s
 user.saved_changes?    262.782k (±12.1%) i/s -      1.290M in   5.028080s
```

activerecord/lib/active_record/attribute_methods/before_type_cast.rb

@@ -46,7 +46,7 @@ module BeforeTypeCast
       #   task.read_attribute_before_type_cast('completed_on') # => "2012-10-21"
       #   task.read_attribute_before_type_cast(:completed_on)  # => "2012-10-21"
       def read_attribute_before_type_cast(attr_name)
-        sync_with_transaction_state
+        sync_with_transaction_state if @transaction_state&.finalized?
         @attributes[attr_name.to_s].value_before_type_cast
       end
 
@@ -61,7 +61,7 @@ def read_attribute_before_type_cast(attr_name)
       #   task.attributes_before_type_cast
       #   # => {"id"=>nil, "title"=>nil, "is_done"=>true, "completed_on"=>"2012-10-21", "created_at"=>nil, "updated_at"=>nil}
       def attributes_before_type_cast
-        sync_with_transaction_state
+        sync_with_transaction_state if @transaction_state&.finalized?
         @attributes.values_before_type_cast
       end
 
@@ -73,7 +73,7 @@ def attribute_before_type_cast(attribute_name)
         end
 
         def attribute_came_from_user?(attribute_name)
-          sync_with_transaction_state
+          sync_with_transaction_state if @transaction_state&.finalized?
           @attributes[attribute_name].came_from_user?
         end
     end

activerecord/lib/active_record/attribute_methods/dirty.rb

@@ -157,12 +157,12 @@ def attributes_in_database
 
       private
         def mutations_from_database
-          sync_with_transaction_state
+          sync_with_transaction_state if @transaction_state&.finalized?
           super
         end
 
         def mutations_before_last_save
-          sync_with_transaction_state
+          sync_with_transaction_state if @transaction_state&.finalized?
           super
         end
 

activerecord/lib/active_record/attribute_methods/read.rb

@@ -39,7 +39,7 @@ def read_attribute(attr_name, &block)
       # This method exists to avoid the expensive primary_key check internally, without
       # breaking compatibility with the read_attribute API
       def _read_attribute(attr_name, &block) # :nodoc
-        sync_with_transaction_state
+        sync_with_transaction_state if @transaction_state&.finalized?
         @attributes.fetch_value(attr_name.to_s, &block)
       end
 

activerecord/lib/active_record/attribute_methods/write.rb

@@ -43,14 +43,14 @@ def write_attribute(attr_name, value)
       # This method exists to avoid the expensive primary_key check internally, without
       # breaking compatibility with the write_attribute API
       def _write_attribute(attr_name, value) # :nodoc:
-        sync_with_transaction_state
+        sync_with_transaction_state if @transaction_state&.finalized?
         @attributes.write_from_user(attr_name.to_s, value)
         value
       end
 
       private
         def write_attribute_without_type_cast(attr_name, value)
-          sync_with_transaction_state
+          sync_with_transaction_state if @transaction_state&.finalized?
           @attributes.write_cast_value(attr_name.to_s, value)
           value
         end

activerecord/lib/active_record/core.rb

@@ -466,7 +466,7 @@ def freeze
 
     # Returns +true+ if the attributes hash has been frozen.
     def frozen?
-      sync_with_transaction_state
+      sync_with_transaction_state if @transaction_state&.finalized?
       @attributes.frozen?
     end
 

activerecord/lib/active_record/persistence.rb

@@ -423,20 +423,20 @@ def _substitute_values(values)
     # Returns true if this object hasn't been saved yet -- that is, a record
     # for the object doesn't exist in the database yet; otherwise, returns false.
     def new_record?
-      sync_with_transaction_state
+      sync_with_transaction_state if @transaction_state&.finalized?
       @new_record
     end
 
     # Returns true if this object has been destroyed, otherwise returns false.
     def destroyed?
-      sync_with_transaction_state
+      sync_with_transaction_state if @transaction_state&.finalized?
       @destroyed
     end
 
     # Returns true if the record is persisted, i.e. it's not a new record and it was
     # not destroyed, otherwise returns false.
     def persisted?
-      sync_with_transaction_state
+      sync_with_transaction_state if @transaction_state&.finalized?
       !(@new_record || @destroyed)
     end
 

activerecord/lib/active_record/transactions.rb

@@ -365,7 +365,7 @@ def with_transaction_returning_status
       status = nil
       self.class.transaction do
         unless has_transactional_callbacks?
-          sync_with_transaction_state
+          sync_with_transaction_state if @transaction_state&.finalized?
           @transaction_state = self.class.connection.transaction_state
         end
         remember_transaction_record_state
@@ -479,7 +479,7 @@ def has_transactional_callbacks?
       # the TransactionState, and rolls back or commits the Active Record object
       # as appropriate.
       def sync_with_transaction_state
-        if (transaction_state = @transaction_state)&.finalized?
+        if transaction_state = @transaction_state
           if transaction_state.fully_committed?
             force_clear_transaction_record_state
           elsif transaction_state.committed?