chore: Add region option to Dialogflow integration (#11510)

## Summary
- support region option when configuring Dialogflow integration
- connect to region endpoint when set
- use session identification based on the region

Fixes: https://github.com/chatwoot/chatwoot/issues/4129

spec/factories/integrations/hooks.rb

@@ -9,7 +9,7 @@ FactoryBot.define do
 
     trait :dialogflow do
       app_id { 'dialogflow' }
-      settings { { project_id: 'test', credentials: {} } }
+      settings { { project_id: 'test', credentials: {}, region: 'global' } }
     end
 
     trait :dyte do