[RomApp] Use NumpyOutputProcess in RomManager rather than RomBasisOutputProcess

[Rbravo555]

📝 Description

For a while, the RomManager contained the following comment:

# FIXME:
# - Use a method (upcoming) for smoothly retrieving solutions. In here we are using the RomBasisOutput process in order to store the solutions

This PR introduces direct snapshot handling inside RomManager, eliminating the reliance on RomBasisOutputProcess and avoiding holding snapshots of a single simulation in RAM unnecessarily.

Note: Future PRs will address the SVD computation for full scalability and usability. In this PR, although snapshots are flushed every step (or at a user-defined interval), they are still loaded back into RAM to compute the SVD. A future PR will introduce an alternative using partitioned methods or libraries like dask or dislib.

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🆕 Changelog

• Refactor: Stopped using RomBasisOutputProcess to store snapshots in RomManager.
• Feature: Implemented SVD logic directly within RomManager (mirroring RomBasisOutputProcess).
• Fix: Modified SetUpSimulationInstance to give precedence to parameters passed by RomManager.