Display depthmaps with FOV metadata

[servantftransperfect]

• Cleanup handling of metadatas in depthMap Visualization
• Add support of depthmaps with only Fov metadata found (Not the MVS one).

See alicevision/Meshroom#2905

[Copilot]

Pull Request Overview

This PR improves depth map visualization by cleaning up metadata handling and adding support for depth maps with FOV (Field of View) metadata. The changes allow the system to fallback to FOV-based camera calibration when the standard MVS (Multi-View Stereo) metadata is not available.

• Refactored metadata parsing into separate functions for better code organization
• Added support for depth maps with "depth_" filename prefix
• Implemented FOV-based inverse projection matrix calculation as fallback

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