Expose and document NMS slider

[samfreund]

Description

The Non-Maximum Suppresion (NMS) Threshold slider is used to filter out overlapping detections. Lower values mean more detections are allowed through, but may result in false positives. It's generally recommended that teams leave this set at the default, unless they find they're unable to get usable results with solely the Confidence slider.

Meta

Merge checklist:

• Pull Request title is short, imperative summary of proposed changes
• The description documents the what and why
• If this PR changes behavior or adds a feature, user documentation is updated
• If this PR touches photon-serde, all messages have been regenerated and hashes have not changed unexpectedly
• If this PR touches configuration, this is backwards compatible with settings back to v2024.3.1
• If this PR touches pipeline settings or anything related to data exchange, the frontend typing is updated
• If this PR addresses a bug, a regression test for it is added