Add missing fields to google_ces_app

[xubolyu-google]

Description:
Add missing public fields to google_ces_app according to google/cloud/ces/v1main/app.proto:

• dashboard_settings
• error_handling_settings
• evaluation_personas
• evaluation_settings
• locked
• vpc_sc_settings
• logging_settings.conversation_logging_settings.retention_window
• predefined_variable_declarations (output only)
• validation_errors (output only)

Issue: https://b.corp.google.com/issues/534420948

ces: added `dashboard_settings`, `error_handling_settings`, `evaluation_personas`, `evaluation_settings`, `locked`, `vpc_sc_settings`, `predefined_variable_declarations`, and `validation_errors` fields to `google_ces_app`

[github-actions]

Googlers: For automatic test runs see go/terraform-auto-test-runs.

@ScottSuarez, a repository maintainer, has been assigned to review your changes. If you have not received review feedback within 2 business days, please leave a comment on this PR asking them to take a look.

You can help make sure that review is quick by doing a self-review and by running impacted tests locally.