Add TSV-backed machine type loader with in-memory cache and fallback warnings

[Ulthran]

Motivation

• Use an authoritative remote machine_types.tsv to resolve Illumina instrument codes instead of a hardcoded map.
• Keep behavior robust when the remote resource is unavailable by falling back to a bundled mapping and warning the user.
• Avoid disk caching and keep a simple in-memory cache for runtime efficiency.

Description

• Add MACHINE_TYPES_FALLBACK (bundled fallback), MACHINE_TYPES_URL, and an in-memory cache _machine_types_cache with a new load_machine_types() loader that fetches and parses the TSV via urlopen and csv and warns on fallback.
• Replace direct uses of the old mapping with calls to load_machine_types() in IlluminaDir._parse_folder, IlluminaFastq.machine_type, and the run-name detection logic.
• Emit warnings.warn messages when the remote TSV cannot be loaded or contains no valid rows, and document the fallback mapping inline with a comment.
• Add necessary imports (csv, warnings, URLError, urlopen) and keep caching only in-memory (no disk writes).

Testing

• No automated tests were run against this change.

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Codex Task

[Copilot]

Pull request overview

This pull request replaces the hardcoded MACHINE_TYPES dictionary with a dynamic loader that fetches machine type mappings from a remote TSV file, with fallback to a bundled mapping when the remote resource is unavailable.

Changes:

• Introduces load_machine_types() function that fetches and caches machine type mappings from a remote TSV URL with fallback to bundled mappings
• Renames MACHINE_TYPES to MACHINE_TYPES_FALLBACK and adds remote URL configuration
• Updates three call sites to use the new load_machine_types() function instead of direct dictionary access

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