Investigate and improve performance of Projects::DependenciesController#index

Why are we doing this work

This endpoint has been reported as underperforming and eating our error budget. See analysis in parent epic.

We must find out where the performance hit comes from and fix it to bring these requests within the acceptable threshold.

Relevant links

Non-functional requirements

• Documentation:
• Feature flag:
• Performance:
• Testing:

Implementation plan

As this Web endpoint shares underlying logic with the dependency list API, this issue must be addressed after #337528 (closed) is completed if any further improvements are deemed necessary.

Parts that are not covered by #337528 (closed)

1. Profile serializer.represent with pagination. Controller action is used always with pagination (check {project path}/-/dependencies requests).