feat(voice): Improved voice call creation flow [EE] (#12268)

This PR improves the voice call creation flow by simplifying
configuration and automating setup with Twilio APIs.

references: #11602 , #11481 

## Key changes

- Removed the requirement for twiml_app_sid – provisioning is now
automated through APIs.
- Auto-configured webhook URLs for:
  - Voice number callbacks
  - Status callbacks
  -  twiML callbacks
- Disabled business hours, help center, and related options until voice
inbox is fully supported.
- Added a configuration tab in the voice inbox to display the required
Twilio URLs (to make verification easier in Twilio console).


## Test Cases
- Provisioning
- Create a new voice inbox → verify that Twilio app provisioning happens
automatically.
  - Verify twiML callback 
- Webhook configuration
- Check that both voice number callback and status callback URLs are
auto-populated in Twilio.
- Disabled features
- Confirm that business hours and help center options are
hidden/disabled for voice inbox.
- Configuration tab
- Open the voice inbox configuration tab → verify that the displayed
Twilio URLs match what’s set in Twilio.

spec/enterprise/controllers/enterprise/api/v1/accounts/inboxes_controller_spec.rb

@@ -24,6 +24,9 @@ RSpec.describe 'Enterprise Inboxes API', type: :request do
       end
 
       it 'creates a voice inbox when administrator' do
+        allow(Twilio::VoiceWebhookSetupService).to receive(:new).and_return(instance_double(Twilio::VoiceWebhookSetupService,
+                                                                                            perform: "AP#{SecureRandom.hex(16)}"))
+
         post "/api/v1/accounts/#{account.id}/inboxes",
              headers: admin.create_new_auth_token,
              params: { name: 'Voice Inbox',
@@ -31,7 +34,8 @@ RSpec.describe 'Enterprise Inboxes API', type: :request do
                                   provider_config: { account_sid: "AC#{SecureRandom.hex(16)}",
                                                      auth_token: SecureRandom.hex(16),
                                                      api_key_sid: SecureRandom.hex(8),
-                                                     api_key_secret: SecureRandom.hex(16) } } },
+                                                     api_key_secret: SecureRandom.hex(16),
+                                                     twiml_app_sid: "AP#{SecureRandom.hex(16)}" } } },
              as: :json
 
         expect(response).to have_http_status(:success)