Add new column "protect_merge_request_pipelines" to "project_settings" table

What does this MR do and why?

• Add a new boolean column protect_merge_request_pipelines to the project_settings table
• To tackle this issue without breaking existing pipelines, we need to add a new project setting called protect_merge_request_pipelines. This MR adds the DB column to store this new project setting.
• Quoting from docs - Changes that should always be a regular schema migration and not be executed in a post-deployment migration include adding a new column to an existing table. So added this as a regular schema migration and NOT a Post Deployment migration

References

• Issue

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