PERF: Avoid saving `ThemeSetting` twice when creating new db override (#26076)

Why this change?

When creating a new theme setting that does not have a corresponding row
in the `theme_settings` table, we end up writing to the database twice
because `ActiveRecord::Base#save!` is called once before the `value`
or `json_value` column is updated again with another database query with
another call to `ActiveRecord::Base#save!`.

What does this change do?

Adds the column to be updated to argument for the `ActiveRecord::Base#create!`
method call so that we only have one write query to the database.

lib/theme_settings_manager.rb

@@ -53,10 +53,10 @@ class ThemeSettingsManager
 
   def value=(new_value)
     ensure_is_valid_value!(new_value)
+    value = new_value.to_s
+
+    record = has_record? ? update_record!(value:) : create_record!(value:)
 
-    record = has_record? ? db_record : create_record!
-    record.value = new_value.to_s
-    record.save!
     record.value
   end
 
@@ -68,16 +68,20 @@ class ThemeSettingsManager
     end
   end
 
-  def has_record?
-    db_record.present?
+  def update_record!(args)
+    db_record.tap { |instance| instance.update!(args) }
   end
 
-  def create_record!
-    record = ThemeSetting.new(name: @name, data_type: type, theme: @theme)
+  def create_record!(args)
+    record = ThemeSetting.new(name: @name, data_type: type, theme: @theme, **args)
     record.save!
     record
   end
 
+  def has_record?
+    db_record.present?
+  end
+
   def ensure_is_valid_value!(new_value)
     return if new_value.nil?
 

lib/theme_settings_manager/objects.rb

@@ -7,10 +7,7 @@ class ThemeSettingsManager::Objects < ThemeSettingsManager
 
   def value=(objects)
     ensure_is_valid_value!(objects)
-
-    record = has_record? ? db_record : create_record!
-    record.json_value = objects
-    record.save!
+    record = has_record? ? update_record!(json_value: objects) : create_record!(json_value: objects)
     theme.reload
     record.json_value
   end