feat(sv-consumer): Add optional db pool size configuration

[luizstacio]

This pull request introduces a new configuration option for managing the database connection pool size and updates the related logic in the application. The changes improve flexibility by allowing users to specify the pool size independently of the number of concurrent tasks.

Configuration Updates:

• services/consumer/src/cli.rs: Added a new db_pool_size argument to the CLI, allowing users to specify the database connection pool size via a command-line argument or environment variable. The help text for concurrent_tasks was also updated for clarity.

Database Initialization Logic:

• services/consumer/src/main.rs: Updated the database setup logic to use the new db_pool_size argument. If db_pool_size is not provided, it defaults to the value of concurrent_tasks.