ULTRA L1b: replace the DE product lookup with the extendedspin priority config

[lacoak21]

Change Summary

closes #3498
closes #3499

Overview

Before this PR, L1b extendedspin read a de-product-lookup ancillary file whose only job was to say which L1b DE product (raw or priority 1–4) to use for each repointing.

This PR replaces it with a new l1b-{sensor}sensor-extendedspin-config ancillary file. Each row applies from its pointing number until the next row's pointing, and holds:

• Priority config: which DE product to use for culling.
• Culling thresholds: one per energy
• Calibration config (cal_config) and an effective date.

This PR also updates how valid events are counted, at each energy bin, we may use a different direct event source. E.g. the last energy bin should always use the priority 0 (raw de) data, otherwise use priority 1 ( some of this logic doesnt make sense to me but its what Bob implemented so im going to ask him about this in the tagup tomorrow)

Testing

Update tests to work with new config file.

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Copilot review overview

🟡 Changes recommended

Configured culling thresholds and DE priorities are not applied consistently, and valid date-only L1B processing is blocked.

Review effort: Balanced
Findings: 2 · 1 · 2

Open (5)

• Require repointing only for extended-spin conversion · New
• Pass configured culling thresholds into processing · New
• Select DE products according to priority configuration · New
• Add distinct p0 and p1 datasets to source-selection tests · New
• Fix misspelled class name in comment · New

[leowerneck]

LGTM.

I left a few optional comments, but I don't think a new review is necessary even if you choose to address them.