oracle: improve submitter, config, and quote APIs

[Rickyy1017]

Summary

• Expose the tracked submitter roster and document its distinction from PriceFeeder role membership.
• Add oracle_config() and field-wise update_oracle_config() with existing validation and cache invalidation.
• Add explicit quote-currency configuration and a getter.
• Document that price_status() already bundles age, stale status, and quorum.

Validation: oracle formatting and editor diagnostics pass. Tests were skipped as requested. Compile checks are blocked because MSVC link.exe is unavailable.

Closes #636
Closes #637
Closes #638
Closes #639

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