AGE-417 : add interface + struct to support otel native integration for postgresql

[mw-advait]

🎯 AGE-417: Add interface + struct support for OTEL native PostgreSQL integration

This PR introduces an interface-based abstraction to support OTEL native integration for PostgreSQL, enabling custom receiver configuration handling while preserving default behavior for other integrations.

The goal is to allow gradual rollout of structured integrations without breaking or refactoring existing map-based integrations.

Summary

• This PR introduces structured support for OTEL native PostgreSQL integration while preserving existing behavior for other integrations.

Changes

• Added Integration interface with UpdateReceiverConfig contract.
• Introduced typed IntegrationConfig and Postgresql configuration structs.
• Implemented PostgreSQL-specific receiver mutation logic, including:
  • Required field validation (username, password)
  • TLS validation
  • Default handling for query and connection pool settings
• Refactored updateConfig to accept IntegrationType and apply integration-aware logic.
• Preserved existing generic merge behavior for non-structured integrations.
• Updated unit tests to reflect new method signature.

Impact

• No breaking changes.
• Existing MongoDB, MySQL, and Redis and all other integrations continue to work as before.
• Establishes foundation for gradual migration to structured, OTEL-native integrations.